Allen and his wife, Katy O'Connell, welcomed a baby boy named Oliver on Tuesday. "Happy Day!!!! My little stud was born today. Oliver is here people!" Allen, 28, tweeted Tuesday night.
The singer also posted a picture of himself in hospital scrubs on Instagram with the caption, "My outfit for the day. The best outfit ill ever where [sic]. #bestdayofmylife."
Allen and O'Connell are high school sweethearts and have been married since 2008.