"It was a complicated match," said Ferrer. "He served well throughout and made it tough for me."
After the fifth-ranked Ferrer controlled the opening set, the local favorite showed some strain from finishing his doubles with partner Juan Carlos Ferrero after midnight Friday.
Dodig rallied to save two break points and force a second-set tiebreaker, where he converted a third set point by forcing the Spaniard into netting his volley.
Ferrer grabbed a 3-1 advantage in the decisive set after Dodig double-faulted. He then hit a running approach shot to break Dodig again before serving out the win in 2 hours, 42 minutes.
"I tried to forget the second set. In the third set I tried to be more consistent because I knew that he was wearing down," said Ferrer. "I knew that in the third I needed to be consistent because so much depended on the first serve and a break could be critical."
Dolgopolov hit nine aces and broke Melzer twice in each set en route to victory.
The 21st-ranked Dolgopolov will now play his fourth career final in search of his second title of the season after winning at Washington.
Ferrer played another doubles later Saturday following the match between Melzer and Dolgopolov.
"Logically, I will be more tired, but whether I win or lose tomorrow won't depend on the doubles tonight," Ferrer said.
He has a chance on Sunday to add the tournament at the City of Arts and Sciences to his five titles this season. He won here on the indoor hard-courts in 2008 and 2010 after losing the final in 2005 when the tournament was played on clay.
Ferrero, a former No. 1 and Valencia native, will retire after this event.