Francesca Buchalski leaned heavily on plastic foam, floral wire and other craft-store staples to assemble evening wear for her first orchestra concert last month at Philadelphia’s Mann Center for the Performing Arts.

The 15-year-old Allentown, N.J., sophomore is part of a new generation of symphony patron that is invigorating the bottom-line performance of concert halls across the U.S. She dressed as Link, the elfin warrior from “The Legend of Zelda,” a series of NintendoCo. videogames that inspired the night’s program.

Francesca Buchalski as Link

Once considered a gimmick, performances featuring videogame music are now a regular part of pops orchestra programming. “You can no longer just sit there and play Beethoven,” said Andrew Litton, music director of the Colorado Symphony and the New York City Ballet Orchestra.

Videogame performances offer a full orchestra—trumpets, harps and other classical instruments—plus choirs and jumbo video screens that synchronize gameplay footage to the music. Costumed attendees—dressed as dragons, wizards, princesses, fairies, knights and sorcerers—often engage in mock battles. Marriage proposals mid-show aren’t unusual; some end with fireworks.

In Philadelphia, the 80-year-old Mann Center has held videogame concerts since 2012. Representatives say the shows attract as many as many as 6,500 attendees, roughly double the average attendance at classical concerts.

The growing popularity has helped offset a decline in U.S. orchestra ticket sales. Over the past decade, such sales have declined at an average annual rate of 2.8%, according to a soon-to-be-published report commissioned by the League of American Orchestras, an advocacy group.

Videogame shows have been instrumental in helping keep the Nashville Symphony afloat as it struggled with the recession and a flood in 2010, said Larry Tucker, vice president of artistic administration: “I would not want to go through a season without it.”

People attending one performance by the 83-member Nashville Symphony plunked down more than $13,000 on action figures, posters, T-shirts and other souvenirs. “Usually if you sell $2,000 or $3,000, it’s a good night for a pops performance,” Mr. Tucker said. “It’s a truly unique audience.”

Stephanie Kibler, a 29-year-old copy writer, went to three performances this summer at concert halls near her home in Fairfax, Va. At one, she said, the audience sang along as the orchestra played the closing theme music from a TV show inspired by “Pokémon,” a videogame where players capture child-friendly monsters and train them for battle.

Last month, Valory Pierce attended a Pokémon-inspired orchestra performance in Portland, Ore. She left the show with a $20 plush doll of a Pikachu, a banana-yellow Pokémon character with rosy cheeks. “You close your eyes and listen to the music and you feel like you’re in an adventure,” the 24-year-old YouTube entertainer said.

Orchestral videogame concerts first gained a following in Japan in the mid-1980s and spread to parts of Europe in the early 2000s. They began appearing regularly in pops repertoires in the U.S. about a decade ago as orchestras sought younger, more diverse audiences.

Unlike classical-music performances, videogame shows feature arrangements that blend looping tracks of music designed to match various moments in a game, such as a slow, eerie medley of piano, percussion and string as the videogame character navigates a castle dungeon.

Videogame company Electronic Arts Inc. has for more than a decade hired such prominent film composers as Hans Zimmer, who won an Oscar in 1994 for “The Lion King.”

Composer Austin Wintory, who worked on the Viking-theme videogame “Banner Saga,” also conducted the Colorado Symphony when it played a live performance of the videogame’s music. He said he was in talks to hire the group to record a sequel. The Colorado Symphony has made the concerts a regular part of its so-called geek series since 2012.

On Tuesday, the world-wide tour of “The Legend of Zelda: Symphony of the Goddesses” stops at the Barclays Center in New York City, where more than 5,000 concertgoers will hear music from the videogame series. The ensemble plans to appear that night on “The Late Show With Stephen Colbert.”

“There’s a lot of rhythmic variety…sentimentality, melancholy, sadness,” said Amy Andersson, who conducts the “The Legend of Zelda: Symphony of the Goddesses” in the traveling tour.

Heidi Harris, the associate concert master for the St. Louis Symphony, was surprised how much she enjoyed performing Zelda in a concert this year. “I thought it was very beautiful,” she said. “I dislike videogames less now.”

Brett Bax, a 19-year-old college freshman, said he attended one of the shows in St. Louis, Mo., to hear songs he has known since grade school. When the orchestra played “Zelda’s Lullaby,” a delicate woodwind melody, “it sent chills down my spine,” he said.

The story of “The Legend of Zelda” isn’t a far cry from such classics as Mozart’s “The Magic Flute.” Both tales involve a brave fellow in a quest to rescue a damsel from a villain’s clutches. In the videogame, the warrior must save Princess Zelda and her peaceful kingdom from Ganon, a half-warlock, half-boar-like creature.

Not every concertgoer is convinced. “From a business-strategy perspective, it completely devalues the brand,” said Roderick Branch, a 39-year-old lawyer in Chicago who attends symphony-orchestra performances about once a week. The very idea, he said, is “akin toMouton Rothschild using its wine to make and sell sangria.”

But consider Mathew Grigsby, a 28-year-old freelance illustrator in Portland, Ore. Twice a year, since about 2008, he said, he has attended symphonic orchestra performances to hear scores from “Mass Effect,” “Halo” and other favorite videogames.

The concerts, he said, inspired him to attend performances of the works by 18th-century artists such as Vivaldi and Mozart.

“I developed a taste for classical music through videogames,” he said.

Write to Sarah E. Needleman at sarah.needleman@wsj.com