The telecoms company says the agreement also includes a two-year pay freeze - until June 2011 - and cuts of around 25% in some staff allowances, such as subsistence and mileage rates.
There will be no performance-related bonuses this year and in the following two years.
Eircom says the deal is the first stage of a restructuring programme, and that further talks on additional measures will start 'immediately'.
The company wants to save €130m a year by 2010/2011.
Cathal Magee, acting group CEO, said the company and union representatives had shown a willingness to make 'difficult but necessary decisions to ensure the long-term competitiveness of Eircom'.
Eircom had signalled that it was seeking more cost cuts when it released half-year results in February.
These showed customer numbers and traffic volumes down for the six months to the end of December.
