The two players had to return to play an extra day on Sunday, with rain suspending all matches the day before.
Humbert – who defeated Jack Draper in the semi-finals – got off to a quick start when play resumed, breaking the Belgian twice in the opening set.
Bergs quickly settled into the tricky conditions on the south coast and raised his game throughout the rest of the match.
He responded brilliantly in the second set, with a pair of breaks in the second and sixth games to force the Frenchman to a decider.
Bergs had the edge in the third set, particularly when returning Humbert’s second serve – winning 57% of the points. The Belgian got the crucial breakthrough at 3-3 and went on to serve out the victory after Humbert hit the net on match point.
It’s a quick turnaround for both players, who will also play each other in the first round of Wimbledon next week.
“I want to congratulate Zizou on your first title, you played really great today,” Humbert added. “I will see you in a few days for the re-match at Wimbledon.
“This tournament is really great. It’s a nice place and to prepare for Wimbledon, it’s a great week for me.”
Elsewhere in the women’s doubles final, top seeds Gabriela Dabrowski and Luisa Stefani defeated Jesika Maleckova and Miriam Skoch 6-1, 6-4.
The Canadian, Brazilian duo – who also made the semi-finals at Roland Garros – will be full of confidence on the grass as they bid to lift the Wimbledon title.