A worker at a branch of the fast-food chain in Linlithgow, West Lothian, was snapped buying 59p bags of the snacks at an Aldi store.
Domino's charges £3.49 per portion for wedges.
When first confronted about the claims, staff initially claimed the food was for personal use.
But pizza bosses then admitted that wedges were sometimes purchased from the nearby supermarket.
A Domino's spokesman said: "Very occasionally some products may run out.
"We do not advocate this as a solution and we have spoken to them to ensure ordering has been adjusted."