The actor told People that he is approached "all the time" by viewers who ask him to divulge plot spoilers.
"I only have one person in my life - she's going to be 70 - who I sit down with before the season starts and tell her everything," he admitted.
"She likes to watch the show with her husband, but she gets too anxious if she doesn't know what's going to happen."
The 59-year-old - who plays Saul on the terrorist drama - also joked about his impressive facial hair, which has attracted much attention from fans.
"For my beard to get really sweet, it takes a minimum of 8 to 10 weeks," he revealed. "But I may not shave it between seasons 2 and 3."
Homeland airs on Showtime in the US and on Channel 4 in the UK.
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Watch a clip from Homeland below: