The gutsy world number 26 from Spain outlasted his tiring compatriot 1-6, 7-6(5), 6-4.
"I don't know what to say. I don't know what I feel. Just like a huge relief," Davidovich Fokina said.
It is a first title at the prestigious 1000 level for the 27-year-old, who extended his winning streak in China to 10 matches after claiming victory at an ATP 250 tournament in Chengdu.
The 20-year-old Jodar, ranked 13 and rising fast, was ruthless to start with.
He reached over his shoulder to save a point before winning it with an overhead smash as he broke for a 2-0 lead.
Davidovich Fokina put pressure on his backhand, but Jodar kept calm as his opponent succumbed to a series of errors.
Jodar broke again to go up 5-1 before closing out the first set after just 27 minutes with an ace.
A fighting Davidovich Fokina refused to go away.
He dropped serve to hand Jodar a 3-2 lead in the second set but finally came up with some answers in the next game, falling on his back to save a point at the net and level at 3-3.
Both men battled to hold serve in a run of intense rallies, with the duo needing to restart a point during the ninth game when a ball rolled onto the court.
Davidovich Fokina was shouting in frustration but saved two break points to go up 6-5 when Jodar returned into the net.
But the younger Spaniard would not crumble, sending down a dangerous backhand to force a tie-break.
The duo were neck and neck, but Davidovich Fokina held his nerve in the tie-break to force a decider.
He was suddenly in control, breaking Jodar's serve in the first game.
His celebration was cut short when Jodar grabbed back a break.
But it went his way again when Jodar fired long to hand the elder Spaniard a 3-2 lead.
Jodar needed a medical timeout for his right thigh as he trailed Davidovich Fokina 4-3.
He buckled in pain as he went for a point during a must-win ninth game, keeping the match alive for a bit longer but needing a trainer for his left thigh at 5-4.
Davidovich Fokina sensed victory and claimed the title on his second championship point.