Van Hecke, who has one year remaining on his Brighton contract, joins Spurs to reunite with manager Roberto de Zerbi, Brighton's former sporting director. Brighton had previously rejected one Tottenham offer before accepting this bid.
The Dutch defender made 131 appearances for Brighton since joining from NAC Breda in 2020, starting 36 of 38 Premier League matches last season as the Seagulls secured an eighth-place finish and European qualification for only the second time in club history.
Tottenham have strengthened their squad with earlier signings of Scotland left-back Andy Robertson from Liverpool and Argentine centre-back Marcos Senesi from Bournemouth, signalling manager de Zerbi's intent to challenge for top-four finishes next season.
Van Hecke's departure weakens Brighton's defensive depth; Tottenham's defensive reinforcements signal intent to compete for Champions League football, affecting their odds and betting on both clubs' domestic league performance.