Tsonga posted a 6-1, 6-2 decision in just 52 minutes over the fifth-seeded Italian, improving to 9-5 all-time in finals and 2-0 this season.
The French crowd favorite also won in Doha to start the year.
He fired seven aces and won 25-of-26 first-serve points en route to the one-sided victory.
Seppi, meanwhile, fell to 2-3 in title matches. He also lost the championship match in Eastbourne this year to American Andy Roddick.