The Argentine defender will join Tottenham Hotspur for the coming season after his contract with the Cherries expired at the end of the 2025-26 season.
Senesi, who joined Bournemouth from Feyenoord in 2022, made 128 appearances during his time on the south coast.
He said: "It’s a very special feeling to be a Tottenham Hotspur player.
"From the first moment, the club has shown why they want me and how much they want me to be a part of what they are building.
"It’s exciting and something I can’t wait to be involved in."
Tottenham had a poor season in the Premier League and only confirmed their survival on the final day, while Bournemouth finished sixth and qualified for the Europa League.
Senesi remained committed to the Cherries and played all but one of the club's league games, with that absence down to suspension.
He provided five assists from centre back - the most from a player in his position in the league.