Documentarian Joshua Z. Weinstein turns to fiction filmmaking with considerable success in “Menashe,” a seriocomic tale of a widower in a Hasidic Brooklyn community who struggles to keep his son with him without having to marry again. Poignant, but shot through with welcome touches of humor, it opens a door to an unfamiliar culture, and does so with honesty and heart.

Portly Menashe Lustig plays the title character, a burly, perpetually unkempt bear of a man whose wife Leah recently passed. A browbeaten cashier, deliveryman and general maintenance guy in a kosher market, he’s the father of Rieven (Ruben Niborski, who looks astonishingly like a young Joseph-Gordon Levitt), who’s alternately charmed by his father’s affection and embarrassed by his out-of-control persona.

Menashe is being pressured by his rabbi (Meyer Schwartz) to remarry, since their community’s practice is that a child must be raised in a two-parent household. If he doesn’t, Rieven will have to move in with his uncle, Leah’s brother Eisik (Yoel Weisshaus), an inflexible but well-off fellow whose opinion of his brother-in-law is hardly positive. Menashe goes on dates arranged for him by the matchmaker, but the one we catch a glimpse of does not go at all well. It’s evident he really doesn’t want to get married again—indeed, he tells a fellow begging on the street that he’d be better off without a wife—and it becomes clear that his relationship with his late spouse was not idyllic (managing to have only a single child was one major problem). Still, unless he takes another wife, Rieven will have to go live with Eisik and his family.

One can’t help but sympathize with Menashe, especially because Eisik is such a stick, but at the same time you have to admit that the fellow is kind of a screw-up. He’s apparently in constant debt to his brother-in-law, and after an accident with a delivery of fish that, in truth, was his fault, you’re likely to believe that the exasperation of his punctilious boss is probably well-grounded. It isn’t that he doesn’t try to clean up his act, especially when it comes to the customary memorial meal for Leah that Eisik wants to host at his home but Menashe insists on having in his tiny cramped apartment. All does not go well, of course, but the rabbi is tolerant of the lapses. Nevertheless his decree about remarriage stands, and Menashe will have to conform or lose his son.

Weinstein makes use of his documentary roots to tell this small but touching story in almost fly-on-the-wall style, with cinematography by him and Yoni Brook that seems spontaneous rather than carefully planned. He also refrains from overexplaining things, preferring to let details of the Hasidic lifestyle to remain somewhat opaque. That’s true of the celebrations—one around a large bonfire—that father and son participate in, but also in a scene as slight as the one in which they select a painting to hang on the wall for the memorial dinner. (Most of the choices are portraits of rabbis.) The result is untidy, but that’s somehow appropriate for a picture about an untidy man.

Lustig rivals Zero Mostel’s Tevye as Menashe, and pulls off in nicely understated style a scene in which he bares his soul in a late-night conversation with a couple of the store’s Hispanic workers, while Niborski captures Rieven’s combination of love for his father and sadness about his antics perfectly. Schwartz and Weisshaus similarly nail the right notes, the former of amiable authority and the latter of prissy rectitude.

The end of Weinstein’s film doesn’t tell us how things will end up for Menashe, but it suggests that he’s going to keep on trying, and you’ll probably walk out of the theatre wishing him—and his son–well.