The actor's wife, LA Thoma, is expecting the couple's first child together.
The two shared a photo of themselves holding their three dogs and a sonogram snap as they broke the news on social media on Thursday (11Feb21).
"Adding one more to the crew! The pups are thrilled," LA captioned the picture.
"Unbelievably excited," her husband added. "As LA noted, the dogs obviously are too."
Grant and LA have been married since 2018.
The parents-to-be were showered with love on social media.
"The Flash" co-star Candice Patton also wrote, "CONGRATS you guys!!!" Another colleague Robbie Amell responded in kind, "Yeah buddy!!! Congratulations!" and cheekily added, "Get your sleeping in now... Cause it's gone soon."
The Pregnancy came roughly two months after Grant and LA celebrated their second wedding anniversary. "That's two years," the actor gushed in mid-December as he shared a throwback picture from his wedding with the female physical therapist. "Love you more now than I did then. Truly. You inspire me to be better everyday. Whether that means doing the dishes in a timely manner or just having more confidence in myself. I don't know who I'd be without you."