Winslow, who hauled down 75 passes for 763 yards and two touchdowns over 16 games for the Tampa Bay Buccaneers last season, is an eight-year NFL veteran.
His agent, Denise White, wrote on her Twitter account, "Congrats to our client @KellenWinslowJr for signing with the Patriots!!!"
Hernandez could be out for as long as six weeks after sustaining a low ankle sprain in Sunday's loss to Arizona.
He has made six grabs for 59 yards and a score so far this the season following a 2011 campaign that saw him haul down 79 passes for 910 yards and seven touchdowns.
Ray Liotta sues skin care company over use of likeness
Boston schools pull out free condoms over wrapping complaints