The Irish National Teachers' Organisation (INTO) has voted in favour of the national pay deal by the tightest margin of any union.
It voted by 51 to 49 per cent to accept the Programme for Prosperity and Fairness (PPF).
About 40 per cent of INTO members voted in the ballot. About 100 branches voted in favour, 46 were against and five were split evenly.
The general secretary of the INTO, Senator Joe O'Toole, said yesterday the result was "very, very tight", but he believed the agreement offered the best way for teachers to have their work recognised.
He said as soon as PPF was approved, teachers would be working to have one of its sections - the new "benchmarking system" - implemented.
He said this mechanism would give teachers a chance to get extra pay increases above those agreed in the deal. He said if the benchmarking system was used properly, teachers could get an increase in pay of up to 30 per cent.
He said he would be seeking a meeting with the other two teacher unions - the Teachers' Union of Ireland (TUI) and the Association of Secondary Teachers, Ireland (ASTI) - to see if they were interested in planning a strategy in relation to the benchmarking body.
Mr O'Toole told members a fortnight ago that if they rejected the deal a ballot for industrial action would have to be taken. This was regarded as a crucial intervention in the campaign by many teachers.
As vice-president of the Irish Congress of Trade Unions (ICTU), Mr O'Toole could have faced the prospect of balloting his members for industrial action over a deal which was accepted by ICTU. This would have put him at odds with ICTU.
The INTO will now cast its 19 votes in favour of the deal when ICTU meets today to decide on its overall position on PPF.
Mr Eddie Conlon, spokesman for Teachers Against the Pay Deal, said the three teacher unions should get together and plan "an alternative pay strategy".