Cllr Tracey replaces Liberal Democrat Tim Cobbett, who stood down earlier this year. She will join fellow KIRG councillor James Giles in representing Green Lane and St James.
Cllr Tracey won 855 votes, ahead of Mahmood Rafiq of the Liberal Democrats, who claimed 647. Labour’s Nick Draper finished third with 265 and the Conservative’s Suniya Qureshi came fourth with 78 votes.
The by-election saw a voter turnout of 40.16%.