Bissouma, 30, has signed a one-year contract in Amsterdam, with the option for another year.
The Malian midfielder was released by Tottenham after his contract expired following the 2025/26 season and has since been without a club.
"Talks with Yves began in August, and we are delighted that he has now signed for us," technical director Jordi Cruyff said.
"In him, we have brought in an experienced player who knows what it takes at the highest level. He can play in several positions and we hope he will be eligible to play as soon as possible."
Ajax had been on the lookout for a free-agent opportunity, with Jordi Cruyff aiming to further strengthen his midfield. The Dutch record champions had an active summer window, making 11 signings, including midfielders Sofyan Amrabat and Julian Brandt.
Ajax are currently fourth in the Eredivisie, trailing leaders and reigning champions PSV by three points after six rounds.
Controversy
During his time in North London, Bissouma was often a target of criticism after several incidents. The Mali international was suspended by the club in August 2024 after posting a video of himself inhaling laughing gas from a balloon.
Bissouma was suspended again in August 2025 for coming late to several team meetings, then-manager Thomas Frank said. Bissouma was caught with laughing gas again in December 2025.
Bissouma signed for Tottenham in 2022 after completing a move from Brighton. The midfielder played 111 games for Spurs, scoring twice and winning the UEFA Europa League in 2025.
