The deal, which is said to be for two years and worth $7 million in guaranteed money, follows reports that Eagles' star running back LeSean McCoy had agreed to sign with the Buffalo Bills.
Drafted in the third round by the 49ers in 2005, Gore has rushed for 11,073 yards with 64 touchdowns. Last season he ran for 1,106 yards in 255 attempts with four touchdowns.
As free agency loomed during the off-season, however, Gore sent a message to the 49ers via Instagram: "I know the fans love me but I need to know if the management does."
The 49ers have reportedly already started looking for other options at running back.