“Baby Duhamel coming soon 🤍,” Mari wrote via Instagram Monday alongside an image of her holding an ultrasound.
Duhamel’s ex-wife Fergie — with whom the actor shares 10-year-old son Axl — chimed in to express her well wishes for the expectant parents.
“I am truly happy for you guys🥰🥰 Axl can’t wait to be a big brother,” the singer commented.
The news comes a year after the two tied the knot in an intimate wedding in Mari’s hometown, Fargo, N.D.
Celebrating the anniversary, Duhamel — who is also a North Dakota native — posted a photo of the couple to his Instagram Story Sunday.
“Happy year 1 my love. You are just the best,” Duhamel wrote atop the smiley selfie. “I love you so much.”
Mari, 29, echoed the heartfelt sentiment, posting an image from their wedding ceremony to her Instagram, writing, “Happy First Anniversary sweet man 🤍 oh how I prayed for you..”
The couple — who were first romantically linked in October 2019 — got engaged just nine months before their big day.
The “Transformers” star popped the question while the two were walking along the beach, sneaking the question into a message-in-a-bottle left on the sand.
“It’s on!! She found a message in a bottle that washed ashore and said YES!!,” Duhamel captioned an Instagram at the time alongside a photo of the two holding up a piece of paper asking if she would marry him.
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While this is the former beauty pageant queen’s first child, Duhamel, 50, shares his son with the “Clumsy” singer.
The former couple — who tied the knot in 2009 after five years of dating — welcomed son Axl Jack in August 2013.
However, the two called it quits four years after his birth.
“With absolute love and respect, we decided to separate as a couple earlier this year,” Fergie, born Stacy Ann Ferguson, and Duhamel said in a statement to Us Weekly at the time.
“To give our family the best opportunity to adjust, we wanted to keep this a private matter before sharing it with the public. We are and will always be united in our support of each other and our family.”
Both the “Shotgun Wedding” star and the “Boom Boom Pow” singer, 48, continue to have a co-parenting relationship with their son, which originally included some ground rules about Duhamel’s dating life prior to his marriage to Mari.
“Fergie, she was very much, ‘No matter what, we have to be civil for Axl,’” Duhamel told Fatherly in a January interview.
“She was very adamant about not letting him meet people I was dating until we’d been dating for six months or something. Or was it four months? I forget. I dated a couple of girls, and he never got to meet them. Which I’m glad.”