The Communication Workers' Union says it is to ballot post office staff about strike action.
The union is at loggerheads with management over this year's public sector pay freeze, with Post Office managers insisting the freeze will apply to its workers.
However, the union argues that, as a company owned by the government and run for profit, its workers should expect a pay rise this year.
The CWU says it has served notice on the Isle of Man Post Office today (Wednesday) about the strike ballot, and more than 250 workers are being asked to cast their vote on whether to start industrial action.
They will get their ballot papers by February 18, and have until March 16 to cast their votes.
The CWU says it's advising members to vote in favour of strike action, saying it's been left with little other option after Post Office management refused to go to arbitration.
At the same time, the union's national official Terry Pullinger is appealing to the Post Office to return to talks, saying it's not too late to settle the dispute.