The party was the biggest loser as the Conservatives took 56 of 75 seats to retain overall control - an increase of 14 compared to the last election in 2013.
Labour lost three seats and the Liberal Democrats two, while Independent candidates gained two seats.
UKIP's Mark Ellis said his party was "not a spent force".
Mr Ellis, who lost his Laindon Park and Fryerns seat, added: "People are listening to Theresa May - and she is pretty UKIP in my opinion - and unfortunately people are thinking UKIP is a spent force, which we are not.
"UKIP is here to stay."
In 2013, the Tories won 42 seats, while UKIP, Labour and the Liberal Democrats took nine seats each.
The Conservatives now hold 56 seats, the Liberal Democrats seven and Labour six. The Canvey Island Independent Party holds two seats, Independents two, Green one and Independent Loughton Residents one.
The Conservatives took all four seats in Harlow, including two from Labour.
Labour's Mike Danvers, who lost Harlow North by nearly 1,000 votes to Tory Michael Garnett, was deputy leader of the Labour group on the county council.
He said he believed he lost because UKIP had not fielded a candidate in the division.
He said: "UKIP people voted Tory. The Tory vote has zoomed up and overtaken me."
Dick Madden, a Conservative cabinet member on the county council who held his Moulsham seat, said: "We did expect to make gains and we hoped we would be increasing our seats."
Mike Mackrory, leader of the Liberal Democrats on the county council, said: "Our number one priority was holding the seats we already had.
"We have managed to do that and increased our majorities on some seats."
The first result in Essex came in shortly after midnight when Kerry Smith, who quit UKIP in 2014, won Basildon Westley Heights with a majority of more than 2,000.
He said the result was a reflection of his "hard work".
John Jowers, the Conservative vice chairman of the county council who held his seat, said the council had "lost some good guys" with the UKIP seat losses.
He said: "You really do need to work together and cooperate in local government - it is not like the green benches in parliament.
"It is often the case that when things get politicized, they go wrong."
UKIP has been wiped off the county map in Essex with the loss of nine seats in Thursday's election.