"She is very gracious, she is very humble, she is always prepared, she is professional she is about her business," Underwood added.
The actor says he told Priyanka that she is "emotionally full".
"It's always fascinating to work with her, because she trusts her emotions and if you look in her eyes there is always an emotion in her eyes without trying to do too much," he said.
Underwood, who is seen playing the role of CIA officer in the show, which airs on Star World, says "what makes this show really work is that you really get into the characters".
"And she sets the tone in terms of the standard of the work we are doing, the depth of the work we're doing," he added.