Djokovic, chasing a sixth title at the event, prevailed 7-6(5) 7-6(6) and will play either Casper Ruud (23) or Andrey Rublev (25) in Sunday's final.
“I had to fight to survive,” the Serbian said after his hard-fought victory over one hour, 54 minutes at the Pala Alpitour in Turin.
“I didn’t feel very reactive today or very comfortable. I knew coming into today’s match from yesterday’s gruelling battle against (Daniil) Medvedev... it would take me some time to adjust and find the dynamic movement I need against Fritz, who is one of the best servers on the tour.
“I am very pleased to have overcome this one as I don’t think it was one of my best days with my tennis but I managed to hang in there.”
If Djokovic wins the final, he will claim the biggest prize in tennis history, cashing in $4,740,300 for lifting the tournament trophy undefeated.