In a funny Twitter message to his 485,000 followers, the former Boyzone singer wrote: "Aggggggggghhhh @missyykeating you're a TEENAGER Happy Birthday !!!!!'" alongside a photo of himself and his actress daughter on Instagram.
He also shared a snap of himself hugging Missu – who turned 13 last Thursday - with the affectionate caption: "A massive Happy Birthday to the coolest TEENAGER. Love you so much. So proud of ya Moo."
Missy's mum, Yvonne - who is divorced from Ronan - also sent her daughter birthday wishes on Twitter, writing: "Big happy birthday to my beautiful1 3yr old daughter Missy. #girlsdayout pic.twitter.com/mZGXxAhVpB"
Ronan, 38, who is a judge on Australia X Factor, and his girlfriend Storm Uechtritz, made bright pink cupcakes for the occasion, using edible disco glitter to decorate heart shape cut outs.
Storm, 32, an Australian television producer, posted photos of the cakes on Instagram, writing: "Been baking love heart cupcakes since 5:30am #FirstAttemptEver."
Named after Ronan's late mother, Marie 'Missy' Keating is the singer's second child alongside older brother Jack, 14, and eight-year-old Ali from his 13 year marriage to Yvonne Connolly.
Missy launched her career in film last year, appearing in Dark Touch and The Sea.