Conservatives, who have been in power for 20 years, lose four seats overall and Labour three as Lib Dems gain five and Hertford elects a Green.
Richard Townsend held All Saints seat in by-election on Thursday triggered by resignation of Dr Louie Corpe.
Nathan Parsad polled 1,504 votes, with Liberal Democrat Emme Vandore second with 564 and Labour's Dawn Newell third with 445.
Eric Buckmaster polled 2,795 votes, over 400 more than in the previous election in 2017, taking a 65% share of the vote, up 3%.
Liberal Democrat Calvin Horner wins Stortford East and town's two winning Conservatives see their votes and majorities drop.
Conservatives hold Stansted and Dunmow but lose Saffron Walden and Thaxted to R4U as Green vote doubles and Lib Dems crumble by a third.
Inspectors who heard appeal against council refusal to let Stansted raise passenger cap allow more comments in light of Govt carbon budget decision.
All 153 seats on Hertfordshire and Essex county councils are being contested plus by-elections in Stortford, Sawbridgeworth and Stansted.
Labour's Philip Ross and Lib Dem Sam North take on Conservative David Lloyd, who has held the post since it was created in 2012.
Alongside Herts County Council and Police and Crime Commissioner polls, there are district and town council by-elections in All Saints ward.
OPINION: Bishop's Stortford Independent news editor Sinead Corr on why putting an X in the box on Thursday (May 6) matters.
Voters in Stansted North will elect not only their Essex county councillor but also a parish councillor on Thursday (May 6).
Residents in Sawbridgeworth will elect not just their Herts county councillor but also a new town councillor in a by-election.
Conservative incumbent John Wyllie beat Liberal Democrat Mione Goldspink by just 80 votes in the 2017 election.
This is the only one of the town's three county council seats where a new face is guaranteed to be elected after Tory Colin Woodward was deselected.