Graf, 28, had not played since undergoing a knee operation shortly after last year's French Open but returned to partner Barbara Rittner to overcome their fellow Germans Meike Babel and Wiltrud Probst,6-3, 6-1, in the first-round doubles match at the WTA tournament.
Graf, who has slipped to 49 in the world although she has a protected ranking of three, shed tears of joy after the 67-minute match as she received a standing ovation from the 3,700 spectators. She is the second seed in the singles, and has a first-round bye.
Graf said: "I felt fine and really enjoyed playing. I tried not to cry but it was too difficult. Eight months out is a long time and I was very nervous. But now I've taken the first step. My knee is in a good state and the doctor did a really good job."
Andre Agassi beat the world No 1, Pete Sampras, 6-2, 6-4, in San Jose, California, on Sunday. Agassi captured his first title in 18 months with a brilliant display of serves, returns of serves and groundstrokes at the Sybase Open. He said after the match that he was aiming at the No 1 ranking this year and looking to fight it out with Sampras in the French Open final.
Britain will play Ukraine in Group One of the Euro-African Zone of the Davis Cup for the second successive year when the two countries meet in Newcastle in April.
Britain's No 1, Greg Rusedski, has dropped one place to No 9 in the latest world rankings, but Tim Henman, the No 2, climbed one place to 17th despite three successive first-round defeats.