A by-election was held in Bootham Ward following the resignation through ill-health of sitting Labour councillor Ken Cooper.
[7] Labour councillor Peter Dodd resigned his Monk Ward seat in 2000 due to ill health.
[8] The seat was won in the by-election by the Liberal Democrat candidate, Nick Blitz.
Following the death of Conservative councillor Bill Bennett in 2007, the Heworth Without seat was won by Liberal Democrat, Nigel Ayre.
[19] Labour Councillor Dr. Roger Pierce resigned in 2010 due to ill health.
The seat was won by the Liberal Democrat candidate and former Council Leader Andrew Waller.
[27] Following talks between the political groups after the election, the Conservatives and Liberal Democrats agreed to run the council as a joint administration.
[27] NB For wards with multiple seats, the total shown is for each party's highest-polling candidate.
Labour Councillor Sophie Kelly resigned for personal reasons triggering a by-election in Hull Road Ward on Thursday, 4 July 2024, the same day as the 2024 United Kingdom general election.
[39] Liberal Democrat councillor Ed Pearson resigned for personal reasons triggering a by-election in Haxby and Wigginton Ward on Thursday, 28 November 2024.