Shanghai - Rafael Nadal tied Andre Agassi for seventh place on the list of all-time Open Era wins when he reached the Shanghai Masters semi-finals on Friday.
Nadal has yet to drop serve in Shanghai.
Dimitrov extended the quarter-final to a third set when he rebounded from a 4-2 deficit to win the second-set tie-breaker.
In the third set, Nadal saved the one break point he faced in the match in the fifth game, and broke serve in the sixth to set up victory.
"Winning a lot of matches in a row, so I'm very happy for everything," Nadal said. "Of course, being able to win the US Open, Beijing, and being in the semi-finals here... I have to try to keep focus and hold that momentum. We'll see tomorrow if I can have another good day."
Fourth-seeded Marin Cilic stands between Nadal and a second ATP final in two weeks.
Cilic advanced to his first Shanghai semi-final by beating Albert Ramos-Vinolas of Spain 6-3, 6-4.
The 25th-ranked Ramos-Vinolas ended Cilic's streak of winning 21 service games in the sixth game of the second set.
"I was a little bit angry with myself just with not keeping up the good tennis at that moment," Cilic said.
The other quarter-finals - Juan Martin del Potro against Viktor Troicki of Serbia, and Roger Federer against Richard Gasquet - are later on Friday.
Results from the ATP Shanghai Masters on Friday (x denotes seeding):
Rafael Nadal (ESP x1) bt Grigor Dimitrov (BUL x6) 6-4, 6-7 (4/7), 6-3
Marin Cilic (CRO x4) bt Albert Ramos-Vinolas (ESP) 6-3, 6-4