Acasuso beat Robredo in the semifinals in Chile last week before losing the championship.
"It was an atypical result, the kind one seldom sees in tennis," Robredo said. "I really played very well today. I feel great."
Robredo won four of his 11 break chances, and saved both by fourth-seeded Acasuso. Robredo will play his 15th ATP final and first since last July at Bastad, Sweden, where the Spaniard won his seventh career title.