More than 65 percent said that their harassment was "severe" including physical threats, stalking and sustained harassment.
ADL CEO Jonathan Greenblatt said in a release: "Online hate causes real harm. Every time someone in an online multiplayer game physically threatens or harasses another player repeatedly because of who they are or what they believe, that experience doesn't just end for that individual when the game is over."
Among online gamers who experience harassment, 53 percent reported being targeted based on their race, religion, ability, gender, sexual orientation or ethnicity, according to the ADL.
Nearly a third have been doxed, which means having their contact or other personal information published online. The ADL also said that some gamers reported being exposed to "extremist ideologies and hateful propaganda".
For each of the 15 online games included in the ADL survey, at least half of the players reported experiencing some form of harassment. The five games where players reported the most harassment were: DOTA 2 (79 percent), Counter-Strike: Global Offensive (75 percent), PlayerUnknown Battlegrounds (75 percent), Overwatch (75 percent) and League of Legends (75 percent).