The top-seeded Russian is seeking his sixth title of the season.
In a high-quality contest, Medvedev committed only 10 unforced errors and saved the three break points he faced, all at 2-1 in the opening set.
He broke his Greek rival's serve at 3-3 and went on to seal the set.
Tsitsipas, relying on his serve and volley game, held his serve under pressure at 3-3 in the second, only succumbing in the tie-break with two forehand errors from 6/6.
Medvedev, who has already secured his ticket to the end-of-season ATP Finals, will be playing in his 36th tour-level final and ninth of 2023.
"In general I am happy with how I served and put pressure on him on a lot of points," said world number three Medvedev.
"I had a lot of opportunities and he played well on them also. Generally, this pressure paid off at the end of the match."
Medvedev has now won nine of his 13 meetings with Tsitsipas.
Sinner edged out Andrey Rublev 7-5, 7-6(5) later on Saturday to reach his sixth final of the season.
The Italian, who beat Medvedev in the Beijing final earlier this month, hit 26 winners in an accomplished display.
Rublev built a 5-2 lead in the first set but Sinner reeled off five straight games to snatch a one-set advantage.
Sinner, at a career-high ranking of world number four, failed to serve out the match in the 10th game of the second set.
Rublev came within two points of forcing a decider in the tie-break, but Sinner held his nerve to win on his first match point.
He will be hoping to make it back-to-back victories over Medvedev, after losing his first six meetings with the former US Open champion.
