Webber of Red Bull Renault finished first at the 78-lap Formula One race at the historic Grand Prix of Monaco circuit.
It was his second win in Monaco and the eighth of his F1 career.
Two-time world champion Sebastian Vettel led until pitting on lap 47, when Webber took over the top spot and held a 1.2-second lead on Mercedes AMG's Nico Rosberg during a light rain on the tight course.
Roberg finished in second place while Fernando Alonso of Ferrari came in third.
Claiming fourth was Vettel, while Lewis Hamilton completed the Top 5.