The 6-foot-6 sophomore guard started 14 games for the Trojans last season, averaging 6.6 points.
"I chose Dayton because I honestly believe in coach (Anthony) Grant and the plan he and the assistant coaches have in place for me," Weaver told Daniels. "They have been doing something special over at Dayton and I just want to be a big part of what’s next to come."
Weaver will sit out the 2020-21 season unless the NCAA grants him a waiver. He has two years of eligibility remaining.
The former four-star recruit was the 37th-ranked prospect on the ESPN 100 for 2018.