The 25-year-old, in his first tour-level final in 16 months, won 7-5 6-1 in one hour and 21 minutes on Sunday.
Edmund, eighth seed at the event, converted his only break point in the first set to edge ahead but demolished his opponent in the second set, seizing control with shots that seemed to get more powerful as the match went on.
Speaking after the victory, he said: "What makes it nice is you experience all those downs and it makes you realise you can't take the success for granted.
"You get the success from having the downs because you learn from that, the low points mentally and the disappointments of losing matches, those help you get to the happy times, the success, the winning the matches.
"I knew that I would have chances because his ball speed is not huge, but it's very hard to get on top of points with him just because the ball comes through low, deep as well.
"It was tough, but the way I had been playing I knew I would have opportunities, especially with my forehand, to get in the points."
He got an early break and took a 3-0 lead in the second set before going on to win it and the match. Seppi left the court to receive treatment at 4-1 and seemed to be slower on his return, making it even harder to chase down Edmund's shots.
Seppi saved a match point but Edmund, whose last success came in Antwerp in 2018, was in fine form with his serve as 11 aces and not facing a single break points demonstrated his superiority.