The result gave the Greens plenty to build on, their leader said
The Greens say they are "disappointed" not to have won more seats in the European elections despite seeing some "spectacular" increases in their vote.
With all results except Northern Ireland declared, the party has won 8.7% of the vote, up from 6.2% in 2004, and retained its two seats.
It pushed Labour into fifth place in both the South West and South East as its vote rose sharply in both regions.
Its leader Caroline Lucas said the outcome boded well for the future.
However, she said the voting system had not properly rewarded her party for the jump in support it had seen.
The party campaigned on a pledge to create a million new jobs in sustainable industries by cutting ID cards and Trident nuclear missile programme and launching "green bonds" to raise finance.
Ms Lucas was re-elected in the South East region of England while Jean Lambert was returned to Brussels from London.
However, despite seeing a near 100,000 increase in its vote in the South East, this was not sufficient to secure a second seat in the largest electoral region as Ukip and the Lib Dems took two seats each and the Conservatives four.
"In the South East we have increased our vote by 50% and we are disappointed it has not translated into a second seat," Ms Lucas said.
"We have seen some spectacular results where we have targeted areas like Brighton and Hove and that bodes well for the next election."
Ms Lucas is fighting Brighton Pavilion at the next election, where the party won 20% of the vote in 2005.