Willis, 22, is facing felony charges of domestic battery by strangulation and grand larceny as well as a misdemeanor charge of coercion, according to the Henderson (Nev.) Police Department website.
The Las Vegas Review-Journal reported the incident involved a 28-year-old woman who called police just after 3 a.m., claiming she had been attacked by her boyfriend. Willis was booked in the afternoon and has a court date scheduled for Wednesday.
Willis was a first-team all-Mountain West performer as a junior this season, averaging a team-best 17.2 points per game and leading the Rebels to the NCAA tournament.
"We have been made aware that a men's basketball student-athlete has been arrested on suspicion of domestic violence and is believed to be in custody," UNLV athletic director Jim Livengood said in a statement. "At this point in time we have no additional information and it would be premature and inappropriate to comment further until this matter has been resolved through the judicial process. In addition, Coach Lon Kruger, who is presently out of town, has been made aware of the situation."
Willis could become the second UNLV player to face disciplinary action this offseason. In April, junior forward Matt Shaw was ruled ineligible to compete in his senior season due to NCAA rules after testing positive for a banned substance.
Diamond Leung covers college basketball for ESPN.com and can be reached at firstname.lastname@example.org.