750 electric vehicles will be delivering post around the country by 2022.
200 e-trikes and electric vans will be making zero emission deliveries by the end of the year.
An Post is also pledging zero emission deliveries in Dublin city centre by the end of 2019.
The pledge covers the areas between the Royal and Grand canals in the capital.
Meanwhile, the environmentally-friendly service will be rolled out in Cork, Galway, Kilkenny, Limerick and Waterford next year.
Other initiatives being rolled out by the company include a trial for public charging points for electric vehicles outside post offices.
20/02/2019. Zero Emission postal deliveries. Pictured (L to R) Keith Lally Dublin Postman and Gemma Lawlor postwoman at Lenister House today. The Minister announced An Post’s Eco Plan, which will see zero emission postal deliveries in a number of cities across Ireland. Photo:Leah Farrell/RollingNews.ie"We're moving away from mail"
An Post CEO, David McRedmond, explained that the volume of parcels being delivered means regular bikes are being phased out.
He observed: "Most of what we'll be doing in the city centres will be electric vehicles... vans.
"The reason why we need them is because we're going to move away from bicycles - we're moving away from mail, and being an e-commerce parcel company.
"An Post is all about delivering parcels."
Climate Action and Environment Minister said An Post is 'taking the lead' in responding to climate change.
He observed: "The public service and our semi-state bodies must be the first to show that it takes policies for sustainability seriously, if we are to persuade the rest of society to make the step changes which we need to make.
"By placing sustainability at the core of their business strategy, [An Post is] leading by example."
It's claimed the new An Post initiatives will save 1,000 tonnes of carbon annually.
