Early in the race, seven riders went on the attack but the sprint teams immediately took control. Some counter-attackers joined the front group 45 kilometres from the finish.
In a soaking-wet finale of the Brussels Cycling Classic, the peloton split to pieces on some technical sections and with ten kilometres left to race, the escapees were caught.
An attentive Caleb Ewan made the selection along with teammate Nikolas Maes and acted as Ewan's leadout during the finale.
It was Pascal Ackermann (BORA-hansgrohe) who started the sprint early and seemed to be heading for his second consecutive win.
Ewan came from behind the big German to sneak past for the win, with Jasper Philipsen (UAE Team Emirates) third.
“I am very happy with the victory during my first participation in this race," said Ewan. "To be honest, I didn’t feel great today and I was struggling on the climbs.
"But once the adrenaline kicked in, it went better. It was a pretty stressful day and also the rain and the narrow roads made it quite a difficult race. There was also a lot of stress in the bunch.
"So, all those things made the race that - I think, usually would be easier - a lot harder. Luckily, the team did a great job to keep me at the front during the difficult moments.”
The Australian sprinter claimed his first win since the final stage of the Tour de France on the Champs Elysees and his tenth win of the season.
“In the end, especially with the slight uphill finish and the headwind, it really was a grind to the finish line," said Ewan. "But I think I just timed my sprint really well. I don’t know if I was the strongest sprinter today but I think I timed it the best and luckily, I still had that little extra in the legs to take the win.”