Thomas, who is 30, had played the last eight seasons with the New Orleans Saints. He visited with the 49ers two weeks ago following news that RB Carlos Hyde had a stress fracture in his foot.
Thomas has 3,745 rushing yards and 28 touchdowns on 818 carries over his NFL career. He also has 2,608 receiving yards and 12 touchdowns on 327 receptions. He played college football at Illinois and was signed as an undrafted free agent by the Saints in 2007.
The 49ers have lost RB Reggie Bush to season-ending MCL surgery. Rookie RB Mike Davis is having surgery on his broken hand today. Starting RB Carlos Hyde's season is in question with a stress fracture in his foot.
On Monday, the 49ers signed former Cleveland Browns RB Shaun Draughn. They also signed RB Jarryd Hayne, who the team waived on Saturday, to the practice squad.
The 49ers' three running backs for Sunday's game against the Atlanta Falcons will likely be Kendall Gaskins, Shaun Draughn, and Pierre Thomas – none of which were on the 53-man roster before Friday.
They will join new starting QB Blaine Gabbert, who replaces a benched Colin Kaepernick. Yesterday, the team also traded TE Vernon Davis to the Denver Broncos.
#NFL Pierre Thomas to the 49ers.
— Lamont Smith (@CLamontSmith) November 3, 2015