Blount was released by the Pittsburgh Steelers on Tuesday for leaving the field early during Sunday's 27-24 win against the Tennessee Titans in Nashville.
The 27-year-old has now made it back to New England, the place he left at the end of last season to join the Steelers on a two-year deal.
He has reportedly signed a two-year contract on the minimum salary for a veteran, plus incentives.
Blount, who played 11 games for the Steelers this season and rushed 266 yards for two touchdowns, will team up with Jonas Gray, who was named the American Football Conference (AFC) offensive player of the week.
Gray, 24, insisted he is not threatened by Blount's arrival, believing the pair can work well together.
"I think we're both going to motivate each other," Gray told reporters after practice on Thursday.
"We kind of knew about each other before, and the guys here have had nothing but good things to say about him.
"The running back position, they always talk about the camaraderie. Right away, even on the practice field, we acted like we’ve known each other for a long time.
"I've heard he was a funny guy, did funny things, pleasure to have around the locker room."
The Patriots boast a 8-2 win-loss record after winning six games in a row.