A statement from 26-year-old Duff's reps says the couple has "mutually decided to an amicable separation. They remain best friends and will continue to be in each other's lives."
It goes on to say they're committed to co-parenting their son Luca, who turns two in March.
Duff first became famous as a Disney star on the series "Lizzie McGuire." She went on to star in films, record music and write books.
Thirty-three-year-old Comrie retired from the NHL in 2012 due to a hip injury.
The news was first reported by E! and People.com.