Mobile operator Meteor has signed a three-year roaming agreement with Vodafone.
Vodafone will supply the Eircom-owned company with 2G and 2.5G (GPRS) roaming services in areas of the west coast.
The deal will come into effect after Meteor's current deal expires at the end of February.
Meteor says its own network now reaches 93% of the population, but the roaming deal will benefit customers in parts of Cork, Kerry, Limerick, Clare, Galway, Mayo, Sligo, Leitrim and Donegal.
Meteor customers in these areas will automatically switch to Vodafone when coverage is lost. There will be no additional cost to the customer, according to Meteor.