Van Hecke, 20, has been a revelation for Dutch side NAC after breaking into their team last season.
Monaco agreed a €2m fee with NAC in June for the centre-back, but the deal stalled over the player’s wishes.
FC Utrecht and AZ held talks in March about signing Van Hecke and he was keen on a move to Utrecht.
Monaco wanted to loan him to Cercle Brugge in Belgium, an idea the youngster did not like.
Brighton will pay just over €2m for Van Hecke and then loan him to Utrecht, making everyone happy.
Depending on how many games he plays for Brighton, the fee for Van Hecke could rise to at least €3m.