The actor, who plays Howard Wolowitz in the sitcom, shared his happy news with ET Online on the red carpet at the Screen Actors Guild Awards in Los Angeles, after his wife displayed a prominent baby bump in her grey gown.
"Yes, my wife is pregnant. I can't take all the credit," he joked.
Simon, 33, and his actress wife Jocelyn Towne are already parents to daughter Adeline, who was born in 2012.
Speaking of fatherhood in May last year, he told TV Fanatic: "For awhile there, I said 'wow, I'm tired.' That hit hard. But it's just every day there's something completely new and amazing and you're watching sort of mirrored evolution in some way. It's actually pretty incredible. You're just watching this little, tiny blob become a person…it's an amazing time."
It's been a happy few weeks for Big Bang Theory castmembers, with Simon's co-star Kaley Cuoco (Penny) marrying tennis player Ryan Sweeting on New Year's Eve.
More celebrities who have announced pregnancies in 2014 below!
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