The Orange County Sheriff's Department said Pasquale was struck about 1:30 a.m.
It wasn't immediately clear whether Pasquale was trying to cross a street. Sheriff's Lt. Gary Strachan said the car's driver stopped, called authorities and stayed with Pasquale until they arrived.
The accident is under investigation. Strachan said no one was arrested.
Pasquale, a redshirt freshman, walked on at UCLA last fall after playing at San Clemente High School, where he was a three-year starter. The 5-foot-7 receiver earned the nickname "Pacman" from his teammates while participating on the scout team in practices last season and again this summer.
"This is a tragic loss," UCLA coach Jim Mora said. "Nick was an outstanding young man who had a positive impact on everyone who knew him. He was a great teammate who was loved and respected by his entire team. Our thoughts are with the Pasquale family."
UCLA said Pasquale played in its season-opening victory over Nevada on Aug. 31, although his name and No. 36 jersey didn't appear on the participation report. The No. 16 Bruins were off this weekend.
Pasquale's teammates reacted on Twitter as the news of his death came out Sunday morning.
"Love you PACMAN. Brother for life. Bruin for Life," Bruins guard Xavier Su'a Filo tweeted. "The definition of a true team player. Came to practice every day ready to work and give his all for his teammates."
Dietrich Riley, a former UCLA safety whose career ended due to injury this summer, tweeted that Pasquale "took every snap on the scout team. Never complained."
"The UCLA family lost a wonderful young man who represented the university, his team and his family well," UCLA athletic director Dan Guerrero said. "Our hearts go out to the Pasquale family, and we will do everything we can to assist and support them, as well as his teammates, as they go through this unthinkable tragedy."