The Spurs didn't disclose financial details of the agreement.
Zeller -- a seven-year NBA veteran -- hasn't played this season. He participated in the Denver Nuggets' training camp but was waived in October.
The Dallas Mavericks selected Zeller in the first round of the 2012 NBA Draft out of North Carolina. The 30-year-old center has averaged seven points, 4.4 rebounds and 0.9 assists per game in his career.
The Spurs have been impacted by injuries and will be without All-Star big man LaMarcus Aldridge when the season resumes at the end of July. Aldridge underwent season-ending shoulder surgery in April.
The 2019-20 NBA season is expected to resume July 30 in Orlando, Fla. Under the league's restart plan, 22 teams will compete at the ESPN Wide World of Sports complex.