The SEC, meanwhile, reprimanded Sterk on Thursday for his comments and fined him $25,000 while also ordering a conference review of South Carolina's game management procedures.
Sterk accused Staley of promoting a hostile and negative atmosphere and said Missouri players were spit on and had racial epithets hurled at them by South Carolina fans after the Gamecocks' 64-54 victory on Jan. 28.
In the suit, filed Thursday in Richland County, South Carolina, Staley cites Sterk's "false, defamatory and reckless" statements. Staley is seeking damages not to exceed $75,000.
"We're not going to let him destroy in one day the sterling reputation she spent a lifetime building," Staley's lawyer, Butch Bowers, said in a statement to The State newspaper.
In a statement announcing the penalties, SEC commissioner Greg Sankey said "there is no place in this league for discord inside or outside of the arena."
"I have had multiple conversations over the past few weeks with representatives of both schools about the problems emanating from their Jan. 28 game, and it has been my desire for those issues to be mutually resolved between the athletic programs and individuals involved," he said. "Unfortunately, a mutual resolution does not appear imminent. Our hope is that we can direct our focus back where it belongs -- on our student-athletes and on-court competition."
Sterk made his comments Jan. 30 on Columbia, Missouri, radio station KTGR.
"We had players spit on and called the N-word and things like that. ... It was not a good environment, and unfortunately, I think Coach Staley promoted that kind of atmosphere. And it's unfortunate that she felt she had to do that," he said.
South Carolina athletic director Ray Tanner said on Jan. 31 that the university had conducted an investigation after Sterk's comments and had found "no confirmation of the alleged behavior directed at the visiting team by fans at the game."
On Feb. 1, responding to the allegations, Staley said, "The accusations are serious and false, and they will be handled in a manner reflective of those facts."
The suit notes that Sterk repeated the allegations in an interview with 101 ESPN in St. Louis on Feb. 1, after South Carolina's investigation had found no evidence to support it.
The lawsuit says Sterk had been given multiple opportunities to retract the statement but had refused to do so. He has made no public comments on the matter since Feb. 1.
"We remain confident in University of Missouri Athletic Director Jim Sterk," Missouri chancellor Alexander Cartwright and University of Missouri system president Mun Y. Choi said in a joint statement. "Since he came here in August 2016, Jim has exhibited a passion for our student athletes and their success and safety both on and off the court. He has proven himself to be an excellent administrator."
Staley's team won the national championship in 2017, and she is a member of the Naismith Memorial Basketball Hall of Fame and coach of the United States women's national team.