The duo was all smiles as they strolled around the music festival in shorts and white tops.
The outing comes two months after Duff's publicist announced their separation.
"They remain best friends and will continue to be in each other's lives. They are dedicated to loving and parenting their amazing son, and ask for privacy at this time," read the statement.
Duff and Comrie married in 2010 and have a 23-month-old son named Luca Cruz.