Current and former Activision Blizzard Inc. employees participated in virtual and in-person walkouts Wednesday to call for changes to the company’s workplace culture amid disappointment with its reaction to allegations made in a recent lawsuit.

The suit, which was filed last week by California’s Department of Fair Employment and Housing, accuses the largest U.S. videogame publisher by market value of paying female employees less than their male counterparts and providing them with fewer opportunities to advance. It also alleges that Activision ignored complaints by female employees of blatant harassment, discrimination and retaliation.

Activision previously said it would fight the charges and that the lawsuit included distorted, and in many cases false, descriptions of its past. Late Tuesday, hours before the planned walkouts, Chief Executive Bobby Kotick said the company hired a law firm to investigate complaints of sexual harassment and gender-pay discrimination.

“Our initial responses to the issues we face together, and to your concerns, were, quite frankly, tone deaf,” Mr. Kotick said in a Tuesday night statement. “It is imperative that we acknowledge all perspectives and experiences and respect the feelings of those who have been mistreated in any way. I am sorry that we did not provide the right empathy and understanding.”

Those steps didn’t go far enough, some employees say, explaining that they didn’t address the need for greater pay transparency to ensure equality nor employee selection of a third party to audit human resources among other things.

More than 3,000 current and former Activision Blizzard workers signed a letter sent to management earlier in the week calling the company’s lawsuit response as “abhorrent and insulting.”

The in-person event was held outside of the Blizzard campus in Irvine, Calif. Across the gaming community, in solidarity with the campaign, people used the hashtag #ActiBlizzWalkout in social-media posts.

Some employees walked out in person Wednesday at Activision Blizzard offices in Irvine, Calif., while others took to social media to protest virtually.

Some employees walked out in person Wednesday at Activision Blizzard offices in Irvine, Calif., while others took to social media to protest virtually.

Photo: Bing Guan/Bloomberg News

Asked about the walkout, a representative for Activision said that the company was committed to fostering a safe, inclusive and rewarding environment for all its employees, and that those who participate won’t be penalized or denied pay.

Former Blizzard software engineer Cher Scarlett said she participated in the virtual walkout by replacing her Twitter profile photos with a plain blue square to bring awareness to the lawsuit and gender bias in gaming. Ms. Scarlett, a 36-year-old Seattle resident, also said she donated $100 to a nonprofit that supports women in the gaming industry.

“I wanted to show my support because I want to see real accountability from current leadership that they haven’t yet shown,” said Ms. Scarlett, who worked at Blizzard from 2015 to 2016.

Current and former Ubisoft Entertainment SA employees signed a separate letter supporting Activision workers, citing previous harassment, discrimination and bullying allegations at their company.

Earlier this month, Paris-based Ubisoft, which makes Assassin’s Creed among other videogames, was accused of institutional sexual harassment in a suit filed in a criminal court in France on behalf of a game-workers union and several employees. A spokeswoman for Ubisoft declined to comment on the suit but said the company doesn’t and won’t tolerate abuse, harassment or discrimination.

“It is clear, from the frequency of these reports, that there is a widespread and deeply ingrained culture of abusive behavior within the industry,” the Ubisoft employees’ letter said.

Activision had roughly 9,500 employees as of the end of last year. Its major units—Activision Publishing, Blizzard Entertainment and King—are known for their Call of Duty, World of Warcraft and Candy Crush videogame franchises, respectively.

Mr. Kotick, who has served as CEO since 1991, said in his statement that he asked law firm Wilmer Cutler Pickering Hale and Dorr LLP to conduct a review of Activision’s policies and procedures “to promote a respectful and inclusive workplace.”

He encouraged anyone with an experience that they believe violates the company’s policies or makes them feel uncomfortable at work to reach out to the law firm, providing an email and phone number for representatives from the company.

In addition to hiring the outside law firm, Mr. Kotick said Activision is adding staff and resources to its compliance and employee relations teams, creating more spaces for employees to share their feedback and evaluating managers and other leaders.

Activision, he said, also would consider a diverse range of candidates for all open positions and remove in-game content that has been deemed inappropriate.

Since the suit was filed, shares in Activision have fallen roughly 6% through Wednesday trading.

Cowen analyst Doug Creutz warned investors in a note Wednesday that employee anger could lead to delays and disruptions to the company’s product pipeline, including critical titles “Overwatch 2” and “Diablo 4.” Last week, Blizzard employee Jeff Hamilton tweeted that “almost no work is being done” on the company’s World of Warcraft franchise “while this obscenity plays out.”

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