Fimmel and Swayze portray FBI agents in the upcoming A&E series "The Beast," which premieres January 15.
Fimmel says Swayze, who was diagnosed with pancreatic cancer earlier this year, didn't miss a day of work during the months-long shoot.
Says Fimmel: "He's just a tough guy and is such a proud guy, and it's amazing - you wouldn't know there's anything wrong with him at all."
The Australian actor said in an interview that Swayze had "good" energy on the set and "wants to come back and do it all again."
Swayze issued a statement this week affirming that so far he's winning his fight against the disease and is responding well to treatment.