Main Post Offices in 85 towns and cities around the country were closed for an hour at lunchtime in a protest of the European Union's plans to open up letter post services to private companies.
Postal workers said the move would see the private companies cherry pick the most lucrative delivery routes.
The workers said it would threaten jobs and could lead to a serious deterioration of services especially in rural area.
Around 10,000 workers at An Post took part in the work stoppage which ended at 2pm.
The An Post group of trade unions has said a proposal to allow the distribution of 'small' mail be opened up to free competition is the final step towards the total liberalisation of the postal service.
The proposal from the European Commission is strongly opposed by unions representing more than two million postal workers across Europe.
The stoppage was aimed at urging the EC to rethink its approach to the issues involved.
To date 14 postal operators have expressed reservations about the proposal.