Lynn Smith, 52, took the dessert home because she had been too busy to finish her lunch during a shift at a Little Chef restaurant in Talke, Staffordshire.
"The majority of national catering businesses in the UK have specific rules surrounding the unauthorised removal of food from premises and Little Chef is no different,” said a spokesperson for Little Chef.
"The tribunal judge accepted that we acted within the bounds of reasonable behaviour and we now consider the issue to be closed."
The roadside chain has banned employees from taking company food off premises and dismissed Smith after catching her leaving with the pie on CCTV. Although she had been given permission to eat the pie, which normally costs £3.99, inside the restaurant, bosses insisted that she knew she was breaking company rules by taking it home.