Ben Platt stars as "Evan" in the Arena Stage production of "Dear Evan Hansen." (Linda Davidson/The Washington Post)

Audiences weep at the new musical “Dear Evan Hansen,” and they shed their tears for Ben Platt. The “Pitch Perfect” movie actor plays an anxious teen whose public profile accidentally goes viral when a “friend” suffers a shocking tragedy.

This world premiere has turned out to be a hit at Arena Stage, and there are several reasons for that. It’s sensitive to its wrenching subject. It’s visually savvy: imagery of social media often swarms the stage. The pop-Broadway score by Benj Pasek and Justin Paul is a warm pathway into the minds of the sympathetic characters; there are no real villains in the tale.

Central, though, is Platt as Evan Hansen, the pulse of the musical’s raw, anxiously beating heart. Post critic Peter Marks called Platt’s performance “most extraordinary.” Director Michael Greif (“Rent,” “Next to Normal,” “If/Then”) testifies to Platt’s “unbelievable emotional accessibility.” Pasek calls the young star “a unicorn.”

“He should not exist,” Pasek says. “It’s difficult to say if he’s a better singer or actor. Our score is more pop than Broadway music, and the way he completely owns that style is so impressive.”

It is poised to reappear at New York’s Second Stage Theatre in spring 2016. “I’m 18 for the next two years, if anyone asks,” says Platt, who turns 22 next month.

(L to R) Ben Platt, Michael Park and Jennifer Laura Thompson in the world-premiere musical Dear Evan Hansen at Arena Stage. (Margot Schulman)

Platt’s career is certainly coming of age. Movie audiences know him as the upbeat misfit Benji in the two “Pitch Perfect” movies, easygoing comedies about college a capella singing groups. He’s now on screen as a gay bartender who adores Meryl Streep’s character in “Ricki and the Flash.”

“To have something on film where I’m looking at Meryl Streep and she’s looking at me and we’re talking to each other,” Platt says, “that’s all you can ask for.”

Not that Platt is only now getting a brush with the big-time. He’s a Hollywood kid whose dad, Marc Platt, was once president of production at Universal Pictures; the senior Platt’s producing credits include the movie “Legally Blonde” and the musical “Wicked.” Because Ben’s parents met doing musicals in college, though, the L.A. household echoed with Broadway cast albums. Bar mitzvahs featured adaptations of show tunes: Ben was feted with a Stephen Sondheim medley that included a parody of “Another Hundred People” that went, “Another hundred playbills just came in through the door.”

Platt followed his three older siblings in a musical theater program where he fell in love with “Oliver!” and “Annie.” By 9, Platt was appearing in annual musical concerts at the Hollywood Bowl, with featured roles in “Mame,” “Camelot” and “The Sound of Music,” co-starring with the likes of Jeremy Irons and Marni Nixon.

By 11, Platt was starring in an eight-month tour of the musical “Caroline, or Change,” the acclaimed Tony Kushner-Jeanine Tesori about a Jewish boy and his family’s African American housekeeper in 1963 Louisiana. The tour sat in Los Angeles and San Francisco with most of the original Broadway cast. “I’d really only ever really been around white Jewish people my whole childhood,” Platt says with a laugh, “so to be around those amazing black singers was really inspiring in terms of the way I like to sing. I grew a lot over those eight months.”

His parents were careful not to shove him into showbiz, and they offered ice cream as bribes for young Ben to go to soccer practice. He was a good student at the private Harvard-Westlake School in Studio City, but he chose Columbia University so he would have access to the New York stages.

Just before fall semester in 2011, though, Platt landed his first movie role as Benji in “Pitch Perfect.” He deferred his Columbia enrollment for a year, but in November 2012 he left school after only two months because he got a break too good to ignore — the role of Elder Cunningham in the Chicago company of “Book of Mormon.” He starred in that for 10 months, then returned to New York for a year-long gig in the same part on Broadway.

"Dear Evan Hansen" with Ben Platt is now playing at Arena Stage. Directed by Michael Greif with music and lyrics by Benj Pasek and Justin Paul. (Courtesy Arena Stage)

This year has been almost entirely dedicated to “Evan Hansen,” except — he nearly blanks on this — for the big Ang Lee movie he shot in Atlanta, “Billy Lynn’s Long Halftime Walk,” based on the Ben Fountain novel. The movie deals with young U.S. soldiers on a victory tour; Platt plays a press rep. The picture (slated for 2016) apparently involves a new refinement of 3-D, but Platt can’t quite describe it. Not his thing, though obviously it could have been.

“It was definitely a choice,” he says. “I think if I had been interested in films, my dad would have been equally supportive. I certainly grew up going to sets and seeing him work, and I knew a certain amount about the film industry. I just never was quite in love with that process.” His dad is a producer on “Ricki and the Flash”; it’s the first time they’ve worked on the same project.

The “Evan Hansen” part has always been Platt’s. Pasek and Paul loved him several years ago when he auditioned for their musical “Dogfight.” He was too young for that show, but the songwriters flagged him for this. “He’s passed a big challenge,” Pasek said days after the opening earned highly encouraging reviews. “That is to be a character that does something that is not necessarily the most likable, and yet we as an audience go along and root for him.”

“Michael and I talked about always making sure that the audience knows what Evan’s intentions are and what’s going on in his mind,” Platt says. “If you feel like you don’t understand him, that’s when you start to not be on his side. That’s the thing that’s so beautiful about this writing: You feel like you really know this kid. And there’s nothing quite like a musical to feel like you understand somebody inside and out.”

Dear Evan Hansen Through Aug. 23 at Arena Stage, 1101 Sixth St. SW. Tickets: $90-$110. Call 202-488-3300 or visit www.arenastage.org .