Dalton Trumbo won an Oscar for writing the 1956 film “The Brave One” — a moniker that should have been bestowed on Trumbo himself.

He didn’t personally accept the award until nearly 20 years later, because he wrote the movie under a pseudonym. Trumbo was one of the most outspoken of the Hollywood Ten, blacklisted for refusing to testify about Communist sympathizers during the Cold War panic that made the First Amendment its biggest victim. Imprisoned for 11 months and barred from working at the peak of his career, he stuck to his ideals when those around him were caving to Congress’ House Un-American Activities Committee.

This blot on American history is hardly a laugh riot of a topic for modern audiences demanding to be entertained. But in the hands of director Jay Roach, best known for such anti-highbrow hits as “Meet the Fockers” and “Austin Powers,” it has enough amusing moments to buoy a story that should never be forgotten.

Top honors for making “Trumbo” a worthwhile trip go to its star, Bryan Cranston, who embodies the witty, mustachioed, righteously bombastic screenwriter so well that you’ll forget about Walter White, the meth-dealing chemistry teacher Cranston will forever be identified with after multiple Emmy wins for “Breaking Bad.”

Hunched over a typewriter in the bathtub while overindulging in lowballs and pills or having heart-to-hearts with wife Cleo (Diane Lane) and smarty-pants daughter Niki (Elle Fanning), Cranston shows Trumbo’s public and private sides — giving full measure to his eccentricities without devolving into caricature.

Strong showings by supporting players include an acidly charming, eternally behatted Hedda Hopper (Helen Mirren), the Hollywood gossip goddess who sided with HUAC and against the Hollywood Ten. Mirren is too likable to be totally convincing as a venomous frenemy, but may be forgiven because she’s so fabulous.

Louis C.K. — cast in what for him is a straight-man role — is appropriately understated as fellow blacklister Arlen Hird. The breakout performance award goes to relative unknown Michael Stuhlbarg as actor Edward G. Robinson, a onetime Trumbo friend and ally who betrays him in favor of getting work. Stuhlbarg brings sophisticated layers of emotion to his portrayal, underscoring that these struggles weren’t cut and dried for everyone involved.

The movie’s primary flaw is not enough time spent re-creating the HUAC hearings and too much on Trumbo’s family life. After a climactic mini-story arc in which Trumbo pits Kirk Douglas (for whom he’s rewriting “Spartacus”) against director Otto Preminger (for whom he’s penning “Exodus”) to see who will spill the beans first and use his real name, the movie unspools into a typical let’s-wrap-up-this-life series of scenes.

If those moments bring on fidgeting, you can always focus on Daniel Orlandi’s costumes. Trumbo’s print short-sleeve shirts, Cleo’s summer dresses and Hedda’s suits will get even the most casual consumer of vintage clothes pining.