The union charges the Santa Monica, Calif., company mistreated workers who protested sexual harassment and discrimination.
“The Communications Workers of America has formally filed [unfair labor practices] charges against the company for worker intimidation and union busting,” the union said in a statement.
The company wasn’t immediately available for comment.
“Activision Blizzard King workers staged a groundbreaking walkout over the summer to draw attention to the disturbing working conditions in the gaming industry at large including, but not limited to, ableist, racist, and sexist cultural practices, workplace discrimination, and pay inequity.”
In addition, “Employees used their social media platforms to organize with one another and share their demands to the world,” the CWA said.
“Instead of responding to these demands, Activision Blizzard management is using coercive tactics to attempt to prevent its employees from exercising their rights to stand together and demand a more equitable, sustainable, and diverse workplace.
“It is their right as workers to organize for a work environment free from abuse, discrimination and sexual harassment, and this right is protected by federal labor law.”
On July 20, the California Department of Fair Employment and Housing filed a workplace discrimination and harassment lawsuit against Activision
The agency said the company has encouraged a "frat boy workplace culture" and consistently paid female employees less than males.
Activision Blizzard stock recently traded at $77.91, up 0.1%.
Morningstar analyst Neil Macker puts fair value at $97 for the stock.
"We are maintaining our current forecasts as we try to better gauge the longer-term impacts of both the lawsuit and allegations on the firm in legal, business, and reputational terms," he wrote.