A.C.O.D. opens Friday at Sundance Cinemas. R, 1:27, three stars out of four.

“A.C.O.D.” is a movie that might properly described as “sitcommy,” although that speaks less to problems with the movie than just how good sitcoms are these days. With sharp writing and acting, including two of the stars of “Parks and Recreation,” “A.C.O.D.” (“Adult Child of Divorce”) is in the tradition of everything from “I Love Lucy” to “Modern Family,” an amusing collision between insufferable people and those who try to suffer them. It’s more a situation than a story, but a pretty funny situation.

For Carter (Adam Scott), that collision has been happening his whole life. His parents’ marriage went up in flames, and ever since their divorce his mom Melissa (Catherine O’Hara) and father Hugh (Richard Jenkins) have been at each other’s throats. Hugh is a serial philanderer who will casually drop personal knowledge about Portuguese whores into a conversation, while Melissa is so tense she seems to vibrate. “You’ve turned a nine-year marriage into a hundred-year war!” Carter tells them.

But he’s a pleaser, and has spent his life navigating around the minefield his parents keep laying for each other, making sure Mom and Dad are never in the same room at the same time, and telling them he does relief work in Honduras over the holidays so he doesn’t have to pick which house to spend Thanksgiving at. By his standards, that’s coping, and he’s gone on to become a restaurant owner (a good job for a pleaser) and a long-term relationship with his girlfriend (Mary Elizabeth Winnstead). Like, really long-term, with Carter in no hurry to get hitched himself.

But Carter’s younger brother, Trey (Clark Duke), was shielded from all the acrimony, so he eagerly proposes to his girlfriend Keiko (Valerie Tian) after only four months, because “we were at the DVD shelf at Costco, and Keiko just said the funniest thing, and I knew I just wanted to spend the rest of my life with this girl.”

Carter is aghast, partially because he thinks his brother is making a huge mistake, partially because a wedding means his parents will have to interact with each other. As we watch, Carter’s carefully managed denial crumbles as he’s put in the middle of one vicious family squabble after another. But the worst may be yet to come — beneath the vitriol, Hugh and Melissa may still have feelings for each other.

Scptt. with his Boy Scout look and sarcastic demeanor, is perfect to play an “adult child,” who has to be the grown-up in his family, but still hasn’t really grown past that nine-year-old kid who had his birthday party ruined when the cops were called in. And Jenkins and O’Hara are both character actor treasures, playing truly awful, self-involved parents who probably deserve each other. Scott’s “Parks and Rec’ co-star Amy Poehler appears in a largely straight role as Hugh’s third wife, and Jane Lynch is very funny as an unlicensed therapist who treated Carter as a child, and secretly turned his private revelations into a book. On the negative side, Jessica Alba also appears as a fellow patient of Lynch’s in a subplot that, boldly, SERVES NO PURPOSE WHATSOEVER.

The screenplay by Ben Karlin, a UW-Madison grad and “Daily Show” producer, and director Stu Zicherman, is sharp and agreeably caustic at times; I wouldn’t be a bit surprised to learn they’re both A.C.O.D.’s themselves, finding the laughs in the new normal of a broken family. Although some of the comedy may hit a little too close to home for their families; they might want to consider doing relief work in Honduras over the holidays.