"We couldn't be happier. The boys have no idea what's in store! #daddysgirl" the actor, 45, wrote on Instagram 
Sean Maguire
Credit: Sean Maguire/instagram

Sean Maguire is going to be a girl dad!

The actor, 45, posted a family photo on Instagram Friday, revealing the exciting news that he and wife Tanya Flynn are expecting a baby girl.

"Very excited to share the news. We are expecting a baby girl," he captioned the sweet photo with Flynn and their two sons Flynn Patrick, 5, and Leo James, 3.

"We couldn't be happier. The boys have no idea what's in store! #daddysgirl ❤️"

Maguire and Flynn, a former police detective, married in Oct. 2012.

On Thursday, Maguire shared a photo of his wife and two boys playing in the ocean in honor of Earth Day.

"Let us all protect Mother Earth," he wrote.

He previously told Sean Maguire Daily that fatherhood has made him think more globally.

"Where it once used to be 'Well, this will do me' you now think of what the world will be like when [you] have a child," said Maguire, who works regularly for Oxfam International and recently organized a benefit in Los Angeles alongside director Julie Anne Robinson that raised money to assist toward the Syrian refugee crisis.

"The first thing I think about when we talk about parenting is the environment. Climate change is a real thing," he added. "Being a parent is providing a safe future for our children and regardless of what your politics are, climate change is not up for negotiation. It's a real thing … So, parenthood has made me feel more responsibility for that."

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After the birth of Leo, Maguire said that older brother Flynn was ready to pass his knowledge onto his sibling.

"Flynn's very excited to meet his little brother and give him cuddles," Maguire told the outlet. "And [he] says he'll 'teach him about Star Wars and football.'"