The 23-year-old TOWIE star and EastEnders actress Jacqueline, 21, both shared a picture of the scan, surrounded by cupcakes and one large cake, which was iced with the message 'twinkle twinkle little star… how we wonder what you are'.
He tweeted a picture of the scan and cakes, writing: "So me and @jacquelineMjos found out the sex of our baby last night.. Take your guess… Pink or Blue inside?? [sic]."
While they haven't yet shared what colour the cake was when they cut into it, Jacqueline sent an overjoyed tweet last night, suggesting she's very happy with the gender.
DAN OSBORNE SHARES REUNION PICTURE WITH TEDDY: "BOY I'VE MISSED YOU!"
She wrote: "Such amazing news today. Life is crazy"
Dan, who is also dad to nine-month-old son Teddy from a previous relationship, recently opened up about how he and Jacqueline make their relationship work.
DAN OSBORNE OPENS UP ABOUT JACQUELINE JOSSA PREGNANCY FOR THE FIRST TIME
He told a British magazine: "It's difficult, but we're [in Ibiza] for work, filming the show. I'm sure there are going to be times when she goes on holiday.
"We have to leave each other and we can't hold each other's hand every day. We Skype. It's a lifesaver."