The 30-year-old had been a free agent since leaving Spurs in June, and BBC Sport understands his contract with the Amsterdam club includes the option to extend for an additional 12 months beyond this season. Ajax technical director Jordi Cruyff said the club had been in talks with the defensive midfielder since August before finalising the move.
"We have brought in an experienced player who knows what it takes to perform at the highest level," Cruyff told Ajax's official website.
"He is capable of playing in several positions, and we hope he will be available for selection as soon as possible."
Bissouma joined Tottenham in 2022 in a high-profile move from Brighton & Hove Albion and went on to make 111 appearances for the north London club. His final season at the club yielded just 11 appearances, all in the Premier League, as Spurs finished 17th for the second consecutive year.
His time in north London was also marked by a disciplinary incident in August 2025, when then-manager Thomas Frank left him out of the squad for the Uefa Super Cup against Paris Saint-Germain because of persistent lateness.
Ajax's move for Bissouma adds further experience to a midfield already reshaped by a busy summer of recruitment, with the club having brought in a host of new faces on both permanent and loan deals. His arrival gives Ajax an established Premier League-calibre option in a deep-lying midfield role, though it remains to be seen how quickly he can force his way into contention after a lengthy spell without regular football.
Ajax's interest in Bissouma had first been reported earlier in the summer, but the Amsterdam club held off making a formal move at the time. With the midfielder still unattached two weeks after the European transfer window closed, Ajax returned to the negotiating table and moved quickly to get a deal over the line, giving Bissouma the chance to resurrect his career following a difficult end to his spell in England.
The Mali international made his name at Brighton before his move to Tottenham, where he was regarded as one of the Premier League's most combative defensive midfielders during his early seasons at the club.
His departure from Spurs closes the book on a mixed four-year spell in north London, and he will now look to rebuild his reputation in the Eredivisie as Ajax push for domestic and European success this season.