The classic featured a 183km route that kicked off in Roeselare.
Anthony Turgis (Direct Energie) placed second, with Bob Jungels (Deceuninck-QuickStep) third.
Fourth across the line was Lukas Pöstlberger (Bora-Hansgrohe), while Tiesj Benoot (Lotto Soudal) completed the podium.
“I had to make sure that nobody came from behind, I just looked when Turgis went,” said Van der Poel.
“I felt there was a sprint in my legs and I just finished it off. It was an instinctive moment really Garcia Cortina reacted and I went with him. I think it was a perfect moment to anticipate everyone else.”
View more results below.
1. Mathieu van der Poel (Ned) Corendon-Circus
2. Anthony Turgis (Fra) Direct Energie
3. Bob Jungels (Lux) Deceuninck-QuickStep
4. Lukas Pöstlberger (Aut) Bora-Hansgrohe
5. Tiesj Benoot (Bel) Lotto Soudal
6. Luke Rowe (GBr) Team Sky
7. Danny van Poppel (Ned) Team Jumbo-Visma
8. Yves Lampaert (Bel) Deceuninck-QuickStep
9. Christophe Laporte (Fra) Cofidis, Solutions Credits
10. Heinrich Haussler (Aus) Bahrain-Merida