The Italian downed De Minaur 6-3, 6-4 to record his 12th win in as many meetings with the Australian.
He faces Alexander Zverev for the title after the German second seed beat Lorenzo Musetti 6-4, 7-5 in the other semi-final.
Sinner, 24, is chasing his fourth title of the campaign following wins at the Australian Open, Wimbledon, and in Beijing earlier this month.
"I came here quite late to the tournament, tried to take every day in the best possible way and I'm happy to be here in the final," said Sinner, the world number two. "It was not easy to (reach) the final here, so I'm very happy.
"I was trying to play some good tennis, trying to serve very well. The first set was very physical, so I'm happy that I won in two sets today."
He is trying to stay in the hunt with Carlos Alcaraz for the year-end number one ranking, with both players in the draw for the final Masters 1000 event of the season in Paris next week.
Sinner retired after suffering from cramps at the Shanghai Masters three weeks ago but has yet to drop a set during his run to the final in Vienna, where he triumphed in 2023.
He had not even faced a break point at the tournament until meeting De Minaur.
Sinner reeled off the first four games in the semi-final before De Minaur clawed a break back, but that didn't prevent the top seed from taking the opening set.
He momentarily allowed De Minaur back into the match in the second set when dropping serve in the sixth game, before breaking again and wrapping up his 20th straight win on indoor hard courts.