Bush confirmed his future plans Saturday in a Twitter posting, saying: “The best is yet to come #49ers.”
The Detroit Lions released Bush last month to save salary cap room, opening the door for the 30-year-old rusher to join his fourth NFL club.
Bush was a college star at Southern California who was drafted second overall by New Orleans in the 2006 NFL Draft. After helping the Saints to their only Super Bowl title, Bush was traded in 2011 to Miami and after being dropped was signed by Detroit in 2013.
Bush has carried 1,266 times for 5,465 yards and 35 touchdowns in his NFL career while also contributing 466 catches for 3,489 reception yards and 18 touchdowns.
Last season, Bush was bothered by a nagging ankle injury and ran only 76 times for 297 yards and two touchdowns while also making 40 catches for 253 receiving yards.
If Bush can avoid health issues, he could pair with returning rusher Carlos Hyde to ease the free agency loss of 49ers running back Frank Gore as well as provide another reception threat out of the backfield for San Francisco quarterback Colin Kaepernick.
The 49ers went 8-8 last season and missed the playoffs for the first time since 2010.