Ciaran Cuffe said it was clear the young people of Ireland want to see change as he heralded "a new beginning" for the Green Party yesterday.
The Dublin city councillor was elected as an MEP for the Dublin constituency and said it was clear his party would have a strong hand in Europe following a spread of support across the continent for the green movement.
He was elected on the 13th count at the RDS last night, finally passing the quota thanks to transfers from Fine Gael's Mark Durkan.
"It is a great day for the Green Party but also a green wave that is sweeping Europe and I think today and this weekend shows that young people want to see change," said Mr Cuffe.
"They have spoken to their parents and grandparents and I think the people have voted for an alternative to business as usual.
"I think this is an auspicious day and I think a new beginning for the Irish Green Party.
"I am looking forward to working in Brussels, in Europe, on climate change, housing and transport, and working closely with my colleagues in the Oireachtas and local authorities."
A delighted Mr Cuffe said it was clear the electorate wanted new policies in key areas, such as housing, transport and the environment.
The surge in support for the party in the build-up to the election showed it was important the Government turns a corner on climate change and implements new policies, he added.
Fine Gael's Frances Fitzgerald followed Mr Cuffe over the line late last night as she secured the second seat in the Dublin constituency.
While Mr Cuffe said the Greens going into Government was "a question for another day", he said it was clear momentum was behind his party colleagues after they secured 48 seats in county and city councils up and down the country.
"I have seen good days and I have seen dark days and I am just so pleased that today is one of the good days and I look forward to building on that success," he said.
"I am just really heartened by the result this evening but I am also heartened by the election of 48 Green Party councillors.
"In local authorities up and down the country, we have a huge opportunity to play a part in transportation and planning issues but more importantly a platform as well to push the parties in Government to change their stance, their policies and to move on to considering climate change - not as an add-on but as an integral part of the policies that are required."
Mr Cuff said last week's elections will bolster the Greens' hand when it comes to influencing policy.
"I think the presence of a strong Green bloc at European level will alter the balance of power in the new European Parliament," he said.
"I think we could well be holding the balance of power there and that will allow us to implement real change on climate change and other issues."
In the race for the remaining two Dublin seats, Fianna Fail's Barry Andrews and Independents4Change's Clare Daly were bolstered by a dip in support for Sinn Fein's Lynn Boylan.
She secured less than half the number of first preference compared with when she topped the poll in 2014.