"I am proud to announce my candidacy for governor of New York so we can bring transformational change that uplifts all New Yorkers,” she said in a statement.
James recounted some of her achievements in a campaign video on Twitter. "I've sued the Trump administration 76 times, but who’s counting?" she said.
James, the state's first Black and first female attorney general, will challenge fellow Democrat Kathy Hochul, the state's first female governor, for the job.
Hochul had been the state's lieutenant governor under Cuomo, ascending to the top job in August when Cuomo resigned. Cuomo's departure came a week after James' office released a report saying that he'd sexually harassed or inappropriately touched 11 women.
Cuomo has denied the allegations, and he and his supporters have charged that the report was a political "hit job." "Tish James used her office to attack the Governor for her own political benefit," Cuomo spokesman Rich Azzopardi said before the announcement Friday.
Cuomo was charged with forcible touching, a misdemeanor sex crime, on Thursday for an incident involving one of the women in the report. James said in a statement afterward that the "criminal charges brought today against Mr. Cuomo for forcible touching further validate the findings in our report."
A Siena College poll on likely challengers in the governor's race last week had Hochul leading the pack, with 31 percent of Democrats saying they'd vote for her, while 17 percent said they'd back Cuomo if he ran again and 14 percent saying they'd back James. With Cuomo out of the equation, 39 percent said they'd vote for Hochul and 20 percent said they'd vote for James.