The meeting is expected to last for several hours and is being held behind closed doors.
The meeting began at around 5.45pm.
Mr Cowen received a significant boost this afternoon when the Minister for Finance Brian Lenihan said he would support the Taoiseach.
Mr Lenihan - who many consider to be a potential leadership candidate - said he 'did not have the luxury of indulging his ambitions', as his priority at present was to put the country first.
Minister Lenihan added that Brian Cowen was the best person to 'lead us into this election'.
However, the Minister for Finance admitted he shared concerns expressed by fellow TD Willie O'Dea that Fianna Fáil might be punished at the polls.
Reacting to Mr Lenihan's decision, Fianna Fáil TD John McGuinness said: 'I think what Brian Lenihan has been saying to you is not what he has been saying to the backbenchers.
'He did encourage dissent, he did encourage us to look at the numbers,' Mr McGuinness said.
Mr McGuinness added that Brian Lenihan 'did express an interest in the leadership, and that is what is shocking about what he has revealed today, because that is not what he had to say to us in the course of last year'.
Fianna Fáil has confirmed it will put a facility in place to allow Minister for Justice Dermot Ahern to vote on the confidence motion from his hospital bed.
Minister Ahern is still recovering in hospital from a hip operation last Friday but expressed his desire to vote on tonight's motion.
Meanwhile, Longford-Westmeath TD Mary O'Rourke said it was too late to look for a change in the leadership of Fianna Fáil.
Speaking on RTÉ Radio, Mrs O'Rourke said there was not over-riding confidence among some parliamentary members in the Taoiseach, but it would not make sense to go into the General Election with a new leader.
Another outgoing TD, Minister for Transport Noel Dempsey has said he has confidence in Mr Cowen to lead Fianna Fáil and the country.
Speaking at a Fianna Fáil selection convention for Meath West last night, Minister Dempsey said there is not a more honest, decent and upright politician in Dáil Éireann.
Mr Dempsey said the Taoiseach has battled with the economic crisis over the last two-and-a-half years.
He said if Mr Cowen has not communicated well enough with the public, it was maybe because he was too busy doing the job he felt had to be done for this country.
Dublin South TD Tom Kitt, who will vote against Brian Cowen this evening, said the result will be tight and the intervention of Minister Brian Lenihan is significant.
He added, however, that a sizeable number of people want change.
Deputy Kitt said the meeting should last two or three hours, and at the end the result will be definite.