The Alphas actor will appear in season two's 17th episode, Entertainment Weekly reports.
Pyper-Ferguson will play Ben, a widower trying to help his son (Benjamin Stockham) overcome the loss of his mother.
The Australian-born Canadian actor's past credits include a role on Caprica and a stint as a series regular on Brothers & Sisters.
It is currently unclear if the character of Ben will have a fairy-tale equivalent - Once Upon a Time co-creators Adam Horowitz and Edward Kitsis previously revealed that iconic figures like Robin Hood, Tarzan and the Wizard of Oz could all appear on the series.
Once airs on Sundays at 8/7c on ABC and will return to Channel 5 in the UK later this year.
> Smallville star Cassidy Freeman joins Once Upon a Time
Watch a promo for the next Once Upon a Time episode below: