On March 10, 2018, just a day after being released by the Seahawks, Sherman agreed to a three-year, $39 million contract with the San Francisco 49ers.

Sherman made his debut with the 49ers in week 1 against the Minnesota Vikings.
 During the game, Sherman recorded 2 tackles and recovered a fumble forced by teammate Fred Warner on Dalvin Cook in the 24–16 loss.

In week 8 against the Arizona Cardinals, Sherman recorded a season high 7 tackles and sacked rookie quarterback Josh Rosen once during the 18–15 loss.

During Week 16 against the Chicago Bears, Sherman was ejected from the game after throwing punches at Bears' wide receivers Josh Bellamy and Anthony Miller, who were also ejected.
The incident was triggered after 49ers' safety Marcell Harris made a late hit on Bears' quarterback Mitchell Trubisky.
On December 29, Sherman was fined $10,026.

Sherman finished his first season with the 49ers with 37 tackles, one sack, four passes defended, and a fumble recovery in 14 games played.
On March 10, 2018, just a day after being released by the Seahawks, Sherman agreed to a three-year, $39 million contract with the San Francisco 49ers.
Sherman made his debut with the 49ers in week 1 against the Minnesota Vikings.  During the game, Sherman recorded 2 tackles and recovered a fumble forced by teammate Fred Warner on Dalvin Cook in the 24–16 loss.
In week 8 against the Arizona Cardinals, Sherman recorded a season high 7 tackles and sacked rookie quarterback Josh Rosen once during the 18–15 loss.
During Week 16 against the Chicago Bears, Sherman was ejected from the game after throwing punches at Bears' wide receivers Josh Bellamy and Anthony Miller, who were also ejected. The incident was triggered after 49ers' safety Marcell Harris made a late hit on Bears' quarterback Mitchell Trubisky. On December 29, Sherman was fined $10,026.
Sherman finished his first season with the 49ers with 37 tackles, one sack, four passes defended, and a fumble recovery in 14 games played.
Richard Sherman (American football)