Pendergraph made the announcement on Tuesday before a workout at Arizona State, his alma mater.
The 6-foot-9 Pendergraph spent the past two seasons at Indiana, mostly in a reserve role. He averaged 3.9 points and 2.8 rebounds per game last season with the Pacers, who reached the Eastern Conference Finals.
Pendergraph was drafted out of Arizona State by Portland in 2009 and played one season for the Trail Blazers before missing the 2010-11 season with a torn right ACL.
He should added frontcourt depth to the Spurs, who lost to Miami in the NBA Finals this past season.
Source: Associated Press