The 37-year-old took out the Trofeo Palma, race one of the Challenge Majorca series in Spain.
McEwen launched his sprint with 300m left and beat Spaniards Koldo Fernandez and former world champion Oscar Freire.
The Australian suffered serious leg injuries last May in a collision during the Tour of Belgium.
“I’m really happy for this victory, it’s my second career after the injury I had last season … (it) is a very important victory for me,” he said on the cyclingnews website.
“For me, the most important thing is that I have no discomfort in my leg, I feel fine and I can compete again with the best”
He was impressive at Adelaide’s Tour Down Under, steadily regaining some form.
He was the best-placed Australian at fourth overall in the Tour.
McEwen has said he wants to keep racing next year, but he will wait until after the Tour de France before deciding on his future.
McEwen is one of Australia’s most talented cyclists, many regard him as one of the most consistent.
– with AAP