"Pics of kids should only come direct from parents," Krasinski, 34, captioned. "So I'm thrilled to introduce you guys to Hazel!!!"
In the adorable snapshot, the couple's baby girl has her right arm raised above her shoulder as she looks up at her proud dad. The blue-eyed and brown-haired tot is wearing a light pink pajama onesie and has a yellow pacifier nearby.
The Office alum and Blunt, 31, tied the knot in July 2010 and welcomed their first child this past February. "Wanted to let the news out directly," Krasinski tweeted at the time. "Emily and I are so incredibly happy to welcome our daughter Hazel into the world today! Happy bday!"
One month later, the British actress debuted her skinny post-baby body while holding hands with Krasinski in L.A. on March 18.
"It's really the coolest thing that's ever happened to me," Blunt said of her pregnancy in the April 2014 issue of Vogue prior to giving birth. "I feel good, although I do wake up feeling like my grandmother."
"I sleep with a fortress of pillows around me," she said, eight months pregnant at the time. "I've got one of those huge C-shaped ones. My husband calls it Gary."