Weatherspoon, a high school teammate of NBA-bound former Buckeye Jared Sullinger and Michigan point guard Trey Burke, played in 25 games last season as Ohio State went 31-8, shared the Big Ten regular-season title and made it to the Final Four before losing to Kansas, 64-62.
The 6-foot-6, 215-pounder averaged 3.0 points and 1.4 rebounds a game while shooting 62 percent from the field and 58 percent on free throws.
The 6-4 Sibert also scored 3.0 points a game and added 1.1 rebounds while hitting 30 percent of his shots from the field and 26 percent behind the arc.
Ohio State spokesman Dan Wallenberg confirmed both transfers on Monday.
Copyright 2012 by The Associated Press
MORE MEN'S COLLEGE BASKETBALL HEADLINES
- Embiid (back) could be out until mid-NCAAs
- Florida, Wichita St. remain 1-2; UK falls out
- Delaware clinches 1st NCAA bid since 1999
- Manhattan wins MAAC, punches NCAA ticket
MOST SENT STORIES ON ESPN.COM
- adidas Men's Michigan Wolverines Maize Tournament Basketball Shorts