The 25-year-old from Quebec won his eighth ATP title here - his third this season after Montpellier and Adelaide.
Neither of these powerful servers conceded a break during the first two sets.
But the Czech Lehecka, who also lost in the final last year, saved two match points in the deciding game of the second set before being broken twice in the final set.
"It’s my first tournament as a married man, and I’m leaving with the trophy - I guess I have to give a bit of credit to my wife for this win," he said after marrying a month ago.
Auger-Aliassime married showjumper Nina Ghaibi in Morocco two weeks after making the quarter-finals of the US Open.
Next up for the winner is the ATP 500 in Basel to try for the world top-8 Masters at the end of the year.
He stands ninth just 340 points behind Lorenzo Musetti, who stands in the eighth qualifying spot for the ATP Finals.