Van Hecke spent the 2021/22 season on loan at Ewood Park, winning Player of the Season after a brilliant campaign.
He then returned to parent club Brighton & Hove Albion, establishing himself as a Premier League player. He started 36 of the Seagulls' 38 top-flight games last term, with his performances catching the eye.
Tottenham have now swooped with Van Hecke, having only one year left on his contract. They've paid a reported £52million for his services, making it the biggest-money deal of the summer so far.
"It's a huge honour to become a Spurs player and when you join such a big club, it's a dream come true," he said.
"I already have a really strong connection with the Head Coach, who I'm looking forward to working with again.
"Micky (van de Ven) has also told me some great things about the Club, so I can't wait to get started.
"I've been at Tottenham Hotspur Stadium as an opposition player and now I'm looking forward to walking out there in front of our fans wearing the Spurs shirt. That will be a special moment."
Head Coach, Roberto De Zerbi, said: "Jan Paul is someone I know very well from our time together at Brighton, and I'm delighted to be working with him again.
"He is a strong, intelligent centre-back who is brave in possession and plays with personality. Those are important qualities for the way I want our team to set-up.
"Off the pitch, he is mature, a leader and has a hunger to learn and improve every day.
"Jan Paul has made great progress over the past few years and I believe he can develop even further here at Tottenham Hotspur."
Van Hecke is currently away with the Netherlands squad as they prepare for their second World Cup game. They drew 2-2 with Japan in their opening game and will play Sweden on Saturday.