The Labour leader predicted that the merger with Democratic Left would see his party growing significantly.
"It provides us with a platform for growth. It is not an end of a journey, it is the commencement of a wonderful, radical voyage," said Mr Ruairi Quinn.
Speaking before the delegates overwhelmingly endorsed the merger on a show of hands, Mr Quinn said Labour would remain a legal entity. "You are not being asked to dissolve 86 years of history."
Mr John Mulvihill, a former TD for Cork East, said not enough time had been provided for all candidates sharing constituencies with DL candidates to speak. Mr Mulvihill will be contesting Cork East at the next election with Mr Joe Sherlock, a former DL TD and senator.
Mr Quinn said he regretted that: "There was a choral practice here this morning, and we could not get into this hall before 1.30 p.m."
The merger had been discussed at five meetings of the general council, which had a representative from Cork East. He had sent out letters to constituency council secretaries, and the party's deputy leader, Mr Brendan Howlin, had visited those constituencies which sought a discussion on the issue.
"We have addressed as best we could the very many legitimate and very real concerns which people in this hall have. I welcome the kind of reservations which have been expressed."
Mr Quinn told delegates earlier that their decision was the most important step Labour could take to build the party into a political force to lead the State into the 21st century. It could provide the Republic with a Labour-led government for the first time.
"The union of Labour and DL marks the end of another political division. It recognises the end of the historic rivalry across Europe among the different parties of the left following the collapse of the Berlin Wall. Today, you have the opportunity to unite the two dominant traditions of the Irish left: Labour and radical republicanism."
In the past, said Mr Quinn, division created tension between members and dismay among supporters. "If this union goes ahead, we will no longer be competing for each other's votes."
Mr Howlin, who led the negotiations with DL, said: "We had come from different routes, but it has become clear that our paths have now converged. Our choice is to build on our common ground or forever to look back at our divided pasts."