"Can't keep it a secret anymore," he captioned the picture of himself and Jacqueline holding a slice of iced pink sponge. "Me and @jacjossa are having a girl!"
EastEnders actress Jacqueline, 22, was quick to retweet her boyfriend's post, adding a series of heart emoticons.
Dan and Jacqueline's exciting news comes two weeks after they set the record straight about their relationship.
After 23-year-old Dan tweeted "relationships just do not seem to work" in November, rumours began to circulate that all was not well with the pair.
In December, however, they put on a united front by posting an sweet picture of themselves kissing on Instagram.
Jacqueline has frequently hit back at her critics on social media and insisted that she is happy.
"I am happy, enjoying my pregnancy," she tweeted. "The ONLY thing that's stressing me out, is reading so much rubbish about 'my life', leave me alone."
The new baby will be Jacqueline's first child. Dan is already a father to his one-year-old son Teddy, whose mother is his ex-girlfriend Megan Tomlin.