The star couple got married at the weekend (September 9) in Mount Pleasant, South Carolina and Badgley - who Lively dated until 2010 - was not aware the ceremony was taking place.
Badgley told People: "I actually didn't know until last night, but I think it's fantastic.
"I couldn't be happier for her."
It has been reported that Florence Welch sung three songs live at the reception, and that a cake for the party was delivered from Virginia.
Lively and Reynolds are said to have been dating since October 2011 following Reynolds's divorce from Scarlett Johansson, although they have been low-key about their relationship.