Now, all parties are saying let bygones be bygones, and a love affair is blossoming in the Bay Area.
The four-time Pro Bowl cornerback visited the 49ers on Saturday and quickly agreed to contract terms with the team, multiple outlets reported.
The deal, which can't be made official until Wednesday, is for three years and worth $39.15 million with a $5 million signing bonus, according to the NFL Network.
Sherman returns to the Bay Area, where he played at Stanford before being taken in the fifth round of the 2011 NFL Draft by the Seattle Seahawks.
During his seven years in the Northwest, a handful of incidents involving Sherman and the 49ers incited bad blood between the two teams.
Some of those occurred on the field, including a game-saving interception in the 2014 NFC Championship Game. Others, like Sherman ripping then-49ers wide receiver Michael Crabtree as "sorry" and "mediocre," took place, off the field.
The brash Sherman also didn't mince words when it came to former 49ers head coach Jim Harbaugh, his coach at Stanford, calling him a bully.
But all seemed forgiven as Twitter reaction from Sherman's former enemies was quick.
Offensive tackle Joe Staley: "As much as I disliked playing against him for years, I know I will love being teammates with him going forward. Pumped to have @RSherman_25 as a teammate!!"
Fullback Kyle Juszcyck: "I take back anything disrespectful I might have said to you in our games before @RSherman_25 ?? Welcome to the squad!!"
Fellow cornerback Ahkello Witherspoon: "@RSherman_25 welcome big dawg!! Let?s get this ...."
Safety Dexter McCoil: "It's lit ... We not playing ... I can't wait to hit the field."
Sherman, who will turn 30 on March 30, is coming off a season-ending Achilles tear, as well as a surgical procedure on his other Achilles.
He was released by Seattle on Friday and had dinner with 49ers head coach Kyle Shanahan that evening.
He had one season remaining on a four-year, $56 million extension he signed in 2014 after the Seahawks won Super Bowl XLVIII.
Sherman has a league-best 32 interceptions since entering the league.