The 17-time Grand Slam winner has looked out of sorts on his favoured clay surface this season, suffering unexpected semi-final exits in Monte Carlo, Barcelona and Madrid, the latter of which was against the Greek youngster just last week.
However, he avenged that loss with an efficient performance which will give him a chance of winning his ninth title in the Italian capital and he will face Novak Djokovic in the final.
It was a day of milestones for Nadal. He extended his record in Rome semi-finals to 11-0 to reach his 50th career Masters 1000 series showpiece, drawing level with Roger Federer's record tally.
Nadal started the encounter on the front foot, breaking Tsitsipas to 15 in the Greek's first service game, then withstanding a tough examination immediately, saving two break points before eventually holding.
Those proved to be the only two break points which Tsitsipas was able to craft out in the entire match. When Nadal broke in the third game of the second, the match was effectively up as the Spaniard dropped just two points on his own serve between going 2-1 up and sealing the set 6-4.
"Finally I won a semi-final," he said after the match.
"I'm happy for that. I'm playing better every match, every week and improving. That's a good feeling, a good personal satisfaction after some not easy moments in terms of injury.
"It's an important victory, an important tournament for me. To be in the final here means a lot."