Charlie is a well-to-do bachelor with a house at the beach, a Jaguar in the front, and an easy way with women. His casual Malibu lifestyle is interrupted when his tightly wound brother Alan, who's facing a divorce, and his son Jake, come to live with him. Together, these two and a half men confront the challenges of growing up; finally. Complicating matters are the brothers' self-obsessed, controlling mother, Evelyn, Alan's estranged wife, Judith and Charlie's crazy neighbor Rose, who wants to be a part of his life and is willing to do anything to be around. After the death of his brother, Alan Harper meets and befriends a lonely young man named Walden Schmidt who turns out to be a billionaire. Unable to afford his brother's home, Alan sells Walden the house, and as a way of showing his gratitude, Walden allows Alan and his son Jake to move in with him.
Charlie's 25-year-old daughter arrives at the beach house, hoping to get to know her family.
Jenny moves in with Evelyn and her wealthy boyfriend, Marty (Carl Reiner).
When Berta hurts her back at work, Alan and Walden think she should retire.
Walden parties with Jenny and her attractive friends; Alan's illicit affair with Lyndsey is jeopardized.
Alan tries to find out what Lyndsey's boyfriend has over him; Walden helps Jenny pursue her acting career.
Alan wants to set up a date with Lynda Carter once he learns Walden knows her; Walden begrudgingly agrees to invite Lynda over for dinner.
Lyndsey's jealousy disrupts Walden's and Alan's dates with beautiful women.
When Alan and Lyndsey's affair puts Walden in danger, he is forced to accept Rose's (Melanie Lynskey) help.
Walden goes on a date with an accident-prone model; Alan's date reveals surprising personal information.
Jake sends Alan a Japanese delicacy; the house comes alive with questionable Christmas lyrics.
Walden teams up with a beautiful former employee (Odette Annable) on a new project; Alan gives Jenny advice about her girlfriend (Aly Michalka).
Lyndsey's boyfriend sets Alan up on a date; Walden wants to help Nicole with her project so she will have time to date him.
Marty Pepper (Carl Reiner) proposes to Evelyn; Alan and Walden plan a bachelor party for Marty.
Alan finds out that Lyndsey broke up with Larry without telling him; Walden tries to prove he is a man's man.
Alan asks Lyndsey to choose between him and Larry; Jenny worries that she and Brooke are growing apart.
Walden thinks his girlfriend is cheating on him; Alan starts dating Larry's sister, Gretchen (Kimberly Williams-Paisley).
Lyndsey finds out about Alan's relationship with Gretchen; Walden has a difficult time telling Barry to find his own place.
Walden's ex-girlfriend invites him to her boutique opening; Gretchen hopes to spend more time at Alan's home.
After reconnecting with Kate, Walden becomes convinced she is the one for him -- until he meets a woman named Vivian (Mila Kunis).
Alan finds an opportunity to make money; Walden addresses his co-dependency issues.
Gretchen insists that Alan reveal his true identity to Larry; Walden, Barry and Jenny go on a road trip.
Alan must face the consequences after revealing his identity to Larry.
Berta causes tension between Charlie and Alan, when she temporarily moves in with them
Charlie wakes up with Rose the morning after her birthday party. Her irate father (Martin Sheen), comes to ask Charlie about what the future holds for him and Rose, but the unexpected happens when Evelyn shows up.
One of Charlie's elderly neighbors tries to seduce Alan, while Charlie tries to stop Jake from giving money to a televangelist.
Charlie helps Alan with his obsession of always having to get approval from the women in his life.
Alan has trouble deciding if he should bring his younger girlfriend to Jake's birthday party to meet his mom and his ex-wife. Rose tries to get her boyfriend to act more like Charlie.
Charlie is nominated for an advertising award, but he decides to boycott it because his arch nemesis always wins. The rest of his family tries to trick him into going. Rose is having relationship problems with Gordon and seeks help from Charlie.
Charlie is surprised to find out that Kandi has been living with them for the last three weeks. Alan is having a tough time helping Kandi earn a living. Charlie has lost his sense because of the dry-spell he is going through.
Alan tries to win Kandi back. Meanwhile, Charlie starts to sleep with her mom, Mandi, and Judith gets set up with her father, Andy.
Jake’s teacher has a meeting with Alan and Judith to discuss the lack of interest Jake has at school. Alan starts to fall for Francine, in a platonic way, because he is tired of the lack of intelligent communication he has with Kandi. Charlie helps Jake audition for his school musical.
Alan is overjoyed by the prospect of Judith remarrying, as he would no longer have to pay alimony. Alan gets Charlie to help him when it looks like the marriage may be derailed due to Jake’s dislike of his mother’s fiancé.
Charlie is dating a woman whose personality and life are like his mother’s.
Alan and Charlie re-examine their sexual identities after Alan befriends Greg, a gay man. Meanwhile, Jake has a crush on Greg's daughter.
Jake gets lucky after Charlie takes him to the racetrack. Meanwhile, Alan has a difficult time at the DMV.
Charlie is shocked when the handyman working on his house beats him out for Chloe's affections. Alan has no sympathy for Charlie’s distress.
Evelyn's boyfriend, Teddy, invites Alan and Charlie to go with him to Las Vegas on his private jet. The boys confront their individual 'daddy issues'
Following a health scare on Halloween, Walden decides to reprioritize his life with Alan's help.
When Walden asks Alan to sign a pre-nup, Alan gets offended and has second thoughts about getting married.
Alan and Walden have a meeting with an adoption social worker that hinges on them being convincing as a loving couple. Lyndsey returns after 60 days in rehab.
A birth mother considers having Walden and Alan adopt her baby.
Walden becomes a foster parent to a 6-year-old boy, but worries about himself when they don't hit it off like he hoped.
Alan breaks Walden's rules when he realizes that Louis thinks he's cool, and he wants it to stay that way.
Alan and Walden befriend three moms at a kids’ gym, but things get complicated when Walden becomes attracted to one of them. Alan goes out for a girls’ night with a group of moms.
Alan and Walden attempt to convince Louis that Santa Claus is real.
Walden discovers how challenging it is to be intimate with women when his foster son, Louis, is in the house. Also, Herb asks Alan if he can go on a date with Lyndsey.
Alan takes it upon himself to help Walden keep Louis after the social worker discovers he and Walden are not really a gay couple.
Walden joins a group for adoptive fathers, and finds it to be a nice escape from Alan.
When Alan breaks up with their social worker to get back together with Lyndsey, Walden worries it will affect Louis’ adoption.
Walden fears if he breaks up with Ms. McMartin, it will jeopardize his adoption of Louis. Also, Alan hesitates when Lyndsey asks him to move in with her.
After they sign their divorce papers, Walden offers Alan the gift of his choice, but when Alan chooses something selfish and impractical, it puts his relationship with Lyndsey on the line.
Charlie Harper is alive. Or is he?
Walden tries to loosen Zooey up by sharing some of Berta's special brownies.
When a huge storm keeps Walden, Alan, Zoey and Lindsay at home on Valentine's Day, conflict brews and relationships are strained.
A near-death experience has an adverse effect on Zoey and Walden's relationship; Alan thinks Lyndsey may have a drinking problem.
Walden's ex-business partner shows up at the beach house looking to make peace.
Alan and Lyndsey introduce their mothers. Jake and Eldridge get a ride from Walden to a party.
Walden breaks the news to Zoey that he is going into business with his ex-wife. Alan and Lyndsey try to cope with their mom's relationship.
Zoey and her daughter move in with Walden; Alan gets more than he bargained for with Lyndsey.
Charlie's ghost pays a visit to Alan after he suffers a minor heart attack.
Zoey isn't convinced Alan deserves all the love and affection he receives upon his return from the hospital.
Jake graduates and must decide what to do with his life.
Upon his release from the hospital, Alan is met with a slew of challenges that test his ability to cope.
Walden hits it off with a British babe, but neither of them is sure he's ready to re-enter the dating world.
Walden is trying his best to impress his new love interest when Bridget reappears in his life.
Walden's mother arrives and Alan is smitten with her, even as she reveals a secret about Walden's past that sends him into a downward spiral.
Walden’s ex-wife and mother try to take control of his company, so he turns to Alan for help.
Zoey tries to convince Walden to cut his hair and shave; Alan and Lyndsey revive their relationship.
When Walden begins redecorating the beach house, Alan becomes overly emotional.
Charlie and Alan hire Berta's sister to cater a party their mother has conned them into throwing for her.
After getting unusually turned down at a bar, Charlie learns that a website has been made dedicated to exposing his lifestyle. Charlie sets out to find who created the site, making amends to all those he stood up, but it's harder than it looks when all the women take the apology better than expected.
Alan is jealous of Charlie when an old classmate, who's now a beautiful woman, seems to be more interested in Charlie.
After an earthquake hits, Judith's house is damaged and she needs a place to stay. So Alan decides to invite her to stay with him and Charlie, without getting Charlie's permission. Charlie isn't happy with this, but accepts it. Alan becomes jealous when Judith goes on a date, and asks Charlie to find him a date, so that he can show Judith that he dates as well.
The brothers throw out their mother, after she insults the way Alan is raising Jake. When Alan and Charlie ignore her phone calls, to get their attention she ends up in the hospital. When Alan and Charlie show up at the hospital they aren't sure if she's faking, and try to call her bluff.
Alan starts to worry about a medical procedure that he is facing, and to get his mind off it, Charlie suggests they go to Las Vegas.
When Judith decides to take a vacation, the brothers have to take care of Jake during the week. Alan finds it challenging, and even forgets to pick up Jake from soccer practice. When Alan finds out that he has to go to the I.R.S. because they're auditing him, he forces Charlie to take care of Jake, and Charlie doesn't do any better then Alan.
After Charlie has back pain, Alan decides to take him to the Hospital. While there Charlie can't stop hitting on the doctor who is examining him. The only problem is that he has a history with her that he can't remember. Berta is feed up with Jake's inability to use the bathroom properly, so she decides to make him clean it until he learns.
Charlie's life turns upside down when his brother and nephew move in; at the supermarket, Charlie discovers he can use 10-year-old Jake to attract women.
While spending time with Jake, Charlie finds it hard to enforce rules that Alan has set out for him. It gets to the point were Jake lures a flock of sea gulls into his room, and Charlie gets very upset. This prompts Jake to try and get Charlie to forgive him. Alan starts doing chores for Judith, in the hopes of them getting back together. During one of the tasks, Judith kisses Alan, leading him to believe that things will get back to the way they once were.
After spending a day at Disneyland, Jake gets sick and wants to go to his mothers' house, to have her take care of him. This sends Alan into a state of misery, as he realizes he's losing his wife, and son. Charlie suggests that they go drinking, and Alan agrees. After drinking the boys take a cab home, but at one point they end up at their mothers, where they try to tell her what they think of her, but fail in getting the point across.
After spending a night in Las Vegas, Charlie decides to live up to his promise that he made to Jake about attending his soccer game. During the game, Charlie sets up a play-date with an unattached mother named Kate, and they hit it off. During one of their dates, Charlie seems like he's ready for a serious relation. Alan sets up a meeting with Gloria (one of the soccer moms) to write a soccer newsletter, but Gloria has other intentions for the evening, and he has no idea. During the evening another soccer mom, Brooke, tries to move in on Gloria's plans.
After meeting Wendy, a one-night stand of Charlies, Jake befriends her. Charlie doesn't like this situation, as he believes Wendy is using Jake to further their relationship, and he has no intention to keep it going. It gets to the point were Wendy even starts spending time with Evelyn, and Charlie becomes desperate to get rid of Wendy. After Charlie breaks it off Jake becomes very unhappy with him, because he won't be able to see Wendy anymore. This forces Charlie to confront Jake and explain the situation as best as he can. Rose sees that Alan knows how to play scrabble, and asks him to teach her to play, he agrees. During the scrabble games the two bond, and Charlie suspects that she is using Alan to get closer to him, but doesn't pursue the issue.
While at the movies, the brothers bump into Judith and her new boyfriend. Seeing that Judith has changed her look, and the fact that Jake doesn't think Alan is as cool as Judith; prompts Alan to realize that if he wants to get back into the dating scene, he's going to have to change his look as well.
Judith believes that Jake is having a hard time dealing with his parent's divorce, after he starts annoying everyone with his non-stop guitar playing. So she suggests that they send Jake to a therapist. Alan doesn't agree at first, but after thinking about it, he believes it might not be such a bad idea.
Walden plans a big surprise for Zoey's birthday.
Walden has a breakdown after his relationship with Zoey ends.
Lyndsey and Alan try to add a little excitement to their love life.
A friend's visiting daughter makes Walden feel his age.
Walden ignores Alan's warnings and starts dating Rose.
Walden must choose between Zoey and Rose.
When Walden gets tired of the complications that come with a traditional relationship, he hires an actress to be his girlfriend; Jake plans a rendezvous with Missi (Miley Cyrus) at the beach house.
Alan feels reluctant to make a commitment to Lyndsey, but an unexpected source inspires him; Walden enjoys being the boy-toy of a wealthy older woman.
Alans famous ex-wife, Kandi, wants to reconcile; when Berta isn't interested in celebrating her birthday, Walden tries to make her day special.
Alan helps Walden create a new identity so he can avoid women who are only interested in his money.
Walden juggles his two identities; Alan ends up alone on Christmas.
Alan invests Walden's money in Kate's fashion line; leading a double life takes its toll on Walden.
Alan and Walden go to Kate's fashion show in New York so Walden can reveal the truth about his identity.
Alan is faced with relationship trouble when he does not give Lyndsey a key to the beach house; Walden, Alan, Herb and Billy commiserate about relationships.
When Jake brings his 36-year-old girlfriend home for a visit, Alan is concerned; Walden tries to hide something from Alan.
Depressed on Valentine's Day, Walden tries to talk Kate into giving him another chance; Alan's holiday plans go south.
When Walden runs into his ex and they start talking about getting back together, Alan worries that she is not good enough.
After a fight with Walden, Alan decides to move in with Herb.
Alan and Walden end up partying too hard as they try to cheer up Herb.
Walden and Alan are caught in the crossfire when Jake cheats on his girlfriend (Jaime Pressly) with her 18-year-old daughter.
Alan has a difficult time coping when Lyndsey breaks up with him.
With encouragement from Walden, Alan decides to update his look; Alan is faced with a moral dilemma when he attracts a married woman.
Walden dates an attractive 22-year-old (Hilary Duff), but ends up being more interested in her grandmother (Marilu Henner); Jake and Alan go on a trip.