The civil lawsuit, first reported by TMZ and confirmed by ESPN, alleges that Kelli Tennant, a former host on Spectrum SportsNet LA -- the Lakers' regional sports network -- received an unwanted physical advance by Walton at a Santa Monica, California, hotel room.
The suit alleges that Tennant, who had a working relationship with Walton stemming from his time as a guest analyst on Spectrum, met with him at the Casa Del Mar Hotel to drop off a copy of her book, for which he provided the foreword, when he was in town on a road trip as an assistant coach with the Golden State Warriors.
According to the legal documents obtained by ESPN, Walton allegedly invited Tennant to his room so they wouldn't be seen together by any Warriors players. He then allegedly pinned Tennant to the hotel bed and forcibly kissed and groped her.
The suit also alleges that in May 2017, sometime after the hotel incident occurred, Walton "forced an aggressive hug" and made a lewd remark about Tennant's outfit at a charity event the two attended.
The Lakers said they were never told of the allegations when Walton was their coach and had no additional comment because he now works for another team.
"At no time before or during his employment here was this allegation reported to the Lakers," the statement read. "If it had been, we would have immediately commenced an investigation and notified the NBA. Since Luke Walton is now under contract to another team, we will have no further comment."
The Kings released a statement on Monday night regarding the alleged incident.
"We are aware of the report and are gathering additional information," the statement said. "We have no further comment at this time."
The Warriors said they were also "aware of the alleged incident" and gathering additional information. The team had no other comment.
The NBA has opened an investigation of its own, sources told ESPN.
The Los Angeles Times reports that Tennant's lawyer declined to say whether she reported the alleged assault to police.
Walton "mutually parted ways" with the Lakers earlier this month, according to the team, and was hired by the Kings the next day.
Team sources told ESPN's Ramona Shelburne that the alleged incident occurred well before Walton joined the Lakers. "No one ever reported it to the team," a source said. "And that is not why the team parted ways with him."