The Green Party took both seats from Labour in the St George Central ward at the local elections in Bristol last month.
Cara Lavan and Abi Finch are now two of 34 Greens at City Hall, where the party will run the council with support from the Lib Dems.
RESULTS: Abi Finch, Green: 1,726 Cara Lavan, Green: 1,496 Sally Bowman, Labour: 1,246 Henry Palmer, Labour:1,041 James Hinchcliffe, Conservative: 283 Justyna Hinchcliffe, Conservative: 248 Alistair Kirtley, Liberal Democrats: 78 Kristopher Barker, Trade Unionist & Socialist Coalition: 70 Brian Hugh Price, Liberal Democrats: 57