Dimitrov had to dig deep after being pushed hard in his quarter-final against Spain's Roberto Bautista Agut, but held out to beat the fifth seed 7-6 (5) 4-6 6-2 in two hours and 29 minutes.
The Spaniard Nadal, 31, was taken to three sets by third seed Dimitrov before running away with the decider, winning their last-four clash 6-3, 4-6, 6-1.
Nadal took immediate control of the third set, racing to a 4-0 lead.
There were frequent flashes of brilliance from Nadal early on, but the match really sprung to life as Dimitrov responded impressively to a nightmare start in the second set.
Nick Kyrgios claimed the scalp of the hottest prospect in tennis in Alexander Zverev on Saturday and then said he was gunning for Rafael Nadal in the China Open final. "I am very pleased the way that I have been playing the whole week, after a very tough first day". But Halep dominated the first set, breaking Ostapenko's serve in the first game at love. I was playing good at the beginning of the second and probably I had nearly match point with those two break points for 3-love. It's the best moment in my life and I want just to keep it. "For me it's an important one and I'm very happy". Nadal eventually converted his second match point as a Dimitrov forehand found the net. "And I have few more dreams in my career". "I think Grigor is a player always with a great attitude, with a positive character".
Nevertheless, the match will be mostly remembered for a point in the second set tie-break. Let's see. I going to try to play my best. "I think it was just a hair or something, a hair from the tennis ball".