Dave, a dealer for Guitar Hero, and Ronnie, a stay-at-home mom, are a typical couple raising two young children in the suburbs of Chicago. They experience various stresses including redecorating their house and raising their kids. Joey and Lucy are high school sweethearts with a smart but naive teenage daughter named Lacey. Their relationship is on the rocks and they are even considering a divorce once Lacey goes off to college. Jason and Cynthia are a neurotic couple who've experienced multiple failed attempts to conceive, and Shane, recently separated (but not legally and officially divorced), has a much younger girlfriend, Trudy.
At Dave's son's birthday party, Jason and Cynthia, using a PowerPoint presentation, announce their troubled marriage and are considering divorce as they cannot have a baby. As a last-ditch effort, they have found a couples therapy resort named Eden. A deal called the Pelican Package is half the normal cost if they can get three other couples to join them. In their presentation, they show photos of sunlit beaches and beautiful locations. They assure the others that the couples therapy is purely optional.
Dave and Ronnie insist they can't go because of their children, declining the trip. In the middle of the night, Jason sets off their alarm to try to sell the idea of the retreat. The commotion wakes the kids, who overheard their parents' conversations of not being able to go because of them. Fearing their parents are contemplating divorce, the kids have already arranged for Dave's father, Grandpa Jim-Jim to babysit so their parents can go to Eden.
The retreat proves to be divided into Eden West and Eden East. West is for couples and uses the tagline "Stay Together". East is for singles and uses the tagline "Come Together". East and West attendees are not allowed to intermingle.
Upon arrival at Eden West, the four couples are shown their villas. At dinner, resort host Sctanley informs them 6 a.m. couples therapy, is mandatory. If any couple fails to attend, it will be taken as an indication that they want to leave, and a refund for Eden will be given, although not for their airfare. The group debates what to do. After an indulgent dinner with many delicacies, they decide to put up with "a couple of hours" of therapy in order to enjoy the other amenities of the resort.
In the morning, each couple meets with an assigned therapist. All four couples are told they have problems, even Ronnie and Dave, who thought they were fine. They endure resort owner Marcel's unusual methods, including swimming with and feeding lemon sharks and yoga sessions with amorous instructor Salvadore.
On the fourth night, Trudy escapes to Eden East. The other seven, encouraged by Joey, leave to find her. After Cynthia and Jason argue, the men and women split up. As they try to find their way to the resort, the men end up arguing and pointing out the problems with each other's marriages.
The women run into Salvadore who takes them to Eden East. The men find the staff lounge where they find Sctanley playing Guitar Hero. He threatens to report them to Marcel, but Dave challenges him to the game (without telling Sctanley that he has helped produce the game). Sctanley, after losing the wager, directs them to Eden East, even though he knows he was tricked by Dave.
When they arrive, Dave realizes what a good thing he has with Ronnie. He goes with her to be alone at a waterfall. Joey finds Lucy with Salvadore and knocks him out, reuniting with her. Cynthia and Jason share drinks and end up becoming intimate. Shane runs into his ex-wife, Jennifer, who admits she still loves him. Shane tells Trudy to remain in Eden East and enjoy being single, then leaves with Jennifer. All four couples return to Eden West.
Vince Vaughn and Malin Åkerman as Dave and Ronnie, a typical suburban couple with two children. Their marriage seems fine, but both realize that Dave tends to undermine Ronnie by crossing emotional boundaries and blocking her needs due to his exhausting work. At the conclusion of their therapy, Marcel grants them the ass as their animal spirit because they are both stubborn, and they bear the burden of not only their troubles but also those of others.
Jon Favreau and Kristin Davis as Joey and Lucy Tanzini, high school sweethearts that have fallen apart due to their belief that they "missed out" on living after high school, having been married and becoming parents immediately after and are contemplating getting a divorce as soon as their daughter goes off to college. They have a daughter named Lacey who is a smart but somewhat rebellious teen. After reuniting in therapy, Marcel gives them a wolf spirit token as they are pack animals but their hearts always lie with their destined mate.
Jason Bateman and Kristen Bell as Jason and Cynthia Smith, a troubled couple whose idea it was to go to Eden with their friends. Their issues stem from a lack of communication complicated with Jason's more controlling methods and their trouble with conceiving a baby. They are a very organized couple and are the most interested in repairing their relationship. Marcel grants them a rabbit token after they reunite, due to their innate ability to overcome any obstacles that stand in their way.
Faizon Love and Kali Hawk as Shane and Trudy, a completely polar opposite couple. Trudy and Shane soon tire of each other due to their differences in age and interests. Trudy goes off to the local single scene, and while attempting to find her and bring her back, Shane and his wife Jennifer reconcile instead. They are given the token of the honeybee to symbolize that while they may visit other flowers from time to time, nothing is as sweet as returning to their hive.
Jean Reno as Marcel, the lead therapist, founder and operator of the resort
Peter Serafinowicz as Sctanley (pronounced Stanley, with a silent "c"), the British manager of the resort who oversees the couples' stay and was the original scoring champion of Guitar Hero on the island. (Vaughn’s DVD commentary explains the silent "c" as simple fun)
Tasha Smith as Jennifer, ex-wife of Shane
Jonna Walsh as Lacey Tanzini
Ken Jeong as Wardo, the therapist of Jason and Cynthia
Amy Hill as Jean, the therapist of Shane and Trudy
John Michael Higgins as Robert John, the therapist of Dave and Ronnie
Carlos Ponce as Salvadore, the yoga instructor
Temuera Morrison as Briggs, the native assistant to Marcel - his name is misspelt as Temeura in the opening credits
Karen David as Spa Attendant
Vince Vaughn's real-life father, Vernon Vaughn, plays his on-screen father.
directed by Peter Billingsley marking his directorial debut,