Luke Walton, the N.B.A. coach who recently left the Los Angeles Lakers and was hired by the Sacramento Kings, has been sued by a former sports broadcaster who said he sexually assaulted her in a hotel room in 2014.

His lawyer called the accusation “baseless” and said it was the work of an “opportunist.”

The lawsuit, filed in Los Angeles County Superior Court on Monday, was brought by Kelli Tennant, a former college volleyball player who worked as a host on Spectrum SportsNet. She detailed her allegation, which was first reported by TMZ, at a news conference on Tuesday.

Ms. Tennant said the assault took place at the Casa del Mar hotel in Santa Monica, while Mr. Walton was working as an assistant coach for the Golden State Warriors.

Mr. Walton had been a mentor and friend whom she had gotten to know through his own work doing sports analysis and through his wife, a former competitive volleyball player, according to the lawsuit. Ms. Tennant visited him while he was in town for a road game to drop off a copy of a book she had published, for which Mr. Walton had written the foreword, according to the lawsuit.