A small number of workers at one of Activision Blizzard Inc.’s studios has voted in favor of unionizing with the Communications Workers of America, a first for a major U.S. videogame publisher and another example of new groups organizing amid a labor crunch.

Twenty-two quality-assurance testers at the studio—Middleton, Wis.-based Raven—took part in the vote Monday in the face of opposition from Activision management. They voted 19 to 3 in favor of organizing.