The 39-year-old Harrison has been active in just five of the Steelers' games this year, despite being healthy.
The team had not announced any transactions Tuesday as of 5 p.m. ET.
After being cut last week to create roster space, and clearing wavers, CBS Sports' Jason La Canfora reported that Harrison visited the Patriots on Tuesday.
Steeler Nation's worst nightmare has become reality: James Harrison is a New England Patriot. Heck, the Chiefs might not even be the team the Patriots face; they might not even see the Steelers, robbing him of a chance to show his former team for most of the past 15 years that they made a mistake in releasing him.
Linebacker James Harrison, the franchise's career sack leader, was released by the team on Saturday. The team also uses linebackers Kyle Van Noy, Trevor Reilly and Marquis Flowers at the end of the line, depending on the package.
The Steelers parted ways with Harrison to make room for tackle Marcus Gilbert.
The Patriots finish the regular season on Sunday, December 31 at home against the New Jets.
Harrison is the Steelers' all-time sacks leader, having played all but one season with the franchise since entering the National Football League in 2004. New England owns the tiebreaker by virtue of its 27-24 win at Pittsburgh on December 17.
The Steelers (12-3) wrapped up their third AFC North title in four years earlier this month and secured a first-round bye by dominating Houston on Christmas night.
Only Pittsburgh, with six, owns more Super Bowl wins.
Pregnant Kylie Jenner and Rob Kardashian Celebrate Christmas With Their Family
The 33-year-old Good American designer filmed them from the chest up, so any signs of a baby bump on Kylie were obscured. Khloe is also expecting her first child with her boyfriend Tristan Thompson and is due to give birth next year.