The Los Angeles Clippers signed forward day contract, the team announced on Monday.
Simmons is averaging 13.5 points and 7.6 rebounds in 21 games for the Reno Bighorns of the NBA D-League.
The nine-year veteran last played in the NBA in 2010-11 with the Spurs, appearing in two games without registering a point.
Simmons previously played with the Clippers for two seasons from 2003-05, recording his best statistical season in 04-05 when he started 74 games and averaged 16.4 points and 5.9 rebounds on his way to earning the NBA's Most Improved Player award.
The DePaul product has played in 437 games with the Wizards, Clippers, Bucks, Nets and Spurs, compiling an average of 9.4 points and 4.0 rebounds per game.