The building on Inchmuir Road has been thoroughly cleaned and remains open as usual.
But some local residents have reported a slight disruption in their mail delivery after receiving their mail on a Sunday after the outbreak.
The latest confirmed cases come after a Royal Mail postage tested positive for Covid-19 at a Fife delivery office in September.
Three colleagues from the Dunfermline office on Woodmill Street were asked to self-isolate after coming into contact with the colleague who tested positive.
A Royal Mail spokesperson said: ‘Royal Mail takes the health and safety of its colleagues, customers and the local communities in which we operate very seriously.
“Ten of our colleagues recently tested positive for the coronavirus at the Bathgate delivery office.
“They are now recovering at home and we wish them a speedy recovery. We carried out an intensive cleaning of the building.
“We are currently processing mail normally in our Bathgate office. The office is open as usual. “