"It's a boy!!!!!!!!!!!!!! Please welcome Dominic Lopez to the world," Mario tweeted Monday, the day of his son's birth.
"Couldn't be happier... Courtney and baby are doing just fine."
Dominic joins big sister Gia Francesca, who turns three-years-old on Wednesday.
The Extra co-host and former America's Best Dance Crew host, 39, and Courtney, 30, announced they were expecting their second child in late February.
Mario and Courtney, who was previously known as Courtney Mazza, were married in an outdoor ceremony in Mexico in December. The event was broadcast on TLC as Mario & Courtney's Wedding Fiesta, a two-hour special, later that month.
The couple met in 2008 when he starred in Broadway's A Chorus Line musical, where she was a dancer, and got engaged in January 2012.
Gia Francesca's birth served as the basis of Mario Lopez: Saved By the Baby, a reality series which aired on VH1 in 2010 and followed Mario and Courtney as they prepared for the birth of their daughter.