The deal is pending a physical. The Giants didn't expect to make a formal announcement until later this week at the earliest, depending on how soon Tejada could get to town for a physical.
Tejada told The Associated Press in the Dominican Republic that he had agreed to the deal.
"I'm very happy and satisfied to reach an agreement with the San Francisco Giants," Tejada told the AP in Spanish. "I take pride in having the opportunity to compete for that team."
Tejada batted .269 with 15 home runs, 26 doubles and 71 RBIs between his two clubs in 2010.
The 36-year-old slugger spent the first seven of his 14 major league seasons across San Francisco Bay as a fan favorite with the Oakland Athletics, winning the 2002 AL MVP award in his second-to-last year with the A's. He left for Baltimore after the 2003 season and has also played for the Houston Astros.
The Padres declined to offer Tejada salary arbitration last week.
The Giants had a void at shortstop after declining to exercise their $9.5 million option on Renteria earlier this month, instead paying him a $500,000 buyout. Then they lost Uribe.
So, finding a reliable replacement in a timely fashion was among general manager Brian Sabean's top priorities.
Renteria is a free agent contemplating retirement after an injury-plagued year, and Uribe completed a $21 million, three-year contract with the rival Los Angeles Dodgers on Tuesday.
The Giants last week brought back first baseman Aubrey Huff on a $22 million, two-year contract. Sabean is trying to keep as much of his roster intact to make another deep postseason run in 2011. San Francisco won the city's first title since moving West in 1958, beating the Texas Rangers in five games.