In his stand-up, Mr. Nanjiani tells longish, confessional tales about, say, his attempts to be cool in school or watching a pornographic videotape in his parents’ home in Pakistan when the power went out. He can’t get the tape out of the VCR, so he decides he has to “pack my bags and walk the earth, which sucks because I love my parents and I’m 12 years old.” Taken out of context, of course, any given sentence in this kind of circuitous, long-form amble doesn’t sound especially funny. But Mr. Nanjiani builds the bit artfully, aided by a stealthy persona that comes across as perfectly ordinary until he deploys a puckish smile, revs up his adenoidal whine and gets his heavy eyebrows dancing.

As he does in his stand-up, Mr. Nanjiani, who immigrated to the United States when he was a teenager, mines the comedy of cultural difference in “The Big Sick” with a light, sharp touch. In another, earlier bit, he talks about a roller-coaster ride, which he calls the scariest experience of his life, adding, “and I grew up in Pakistan.” In the movie, he drops a few terrorist-themed jokes so lightly that you’re caught off guard as much by his casual delivery as by the actual gags. You sense that he’s probably heard every ugly joke about Muslims imaginable, and so he’s learned how to get there first, staking a claim on a contested subject, finding humor and strength in other people’s stupidity.

In some ways, “The Big Sick” plays like an extended version of one of Mr. Nanjiani’s anecdotal tales, though one streaked in tears and featuring a cast that includes the perfectly paired Holly Hunter and Ray Romano as Emily’s parents. Mr. Showalter, whose movies include “Hello, My Name Is Doris,” isn’t much of a visual stylist — the look of this movie is basically functional plus — but he’s terrific with actors and understands that even minor characters should be people, not background. In “The Big Sick,” you vividly see the person in each role, from nurse (Myra Lucretia Taylor) to would-be bride (Kuhoo Verma), which enriches the emotional texture and underlines that there’s something at stake.

Ms. Kazan’s work here is pivotal, especially given that she needs to make a lasting, expressive impact with Emily before the character disappears, and the narrative center of gravity shifts squarely to Kumail. In other words, you need to fall for Emily as much as Kumail does while she pokes and prods him, encouraging him to come out and play. When he’s offstage, Kumail can seem as if he were waiting for something to happen, and when her parents arrive in Chicago, he recedes, turtle-like, creating a recessiveness that makes some of his deadpan discomfort even squirmier. Mostly, Mr. Nanjiani and Ms. Kazan look and sound — and, importantly, feel — like people, like people you know and might fall for.