[4] In October 2021, Cardiff Council accepted a number of ward change proposals for the next election made by the Local Democracy and Boundary Commission for Wales, with only slight modification.

In 2019, three by-elections (Ely, February 2019; Cyncoed, July 2019; and Whitchurch & Tongwynlais, October 2019) were called following the deaths of the sitting councillors.

[9][10] In March 2018, Cllr Neil McEvoy was expelled from Plaid Cymru after allegedly disruptive behaviour at the party's 2017 spring conference.

[11] Following the controversy, in October 2019, the three remaining Plaid Cymru councillors resigned their whips, and formed an independent group with McEvoy.

[15] The Welsh Cladiators, a residents group campaigning against fire defective buildings, hoped to stand in the Butetown ward, but ultimately did not.

[16] In September 2021, Plaid Cymru and the Green Party announced an electoral pact which would see them fielding a joint slate of candidates in Cardiff.

[20] They won two seats, both in the Pentyrch and St Fagans ward,[21][22] while the Liberal Democrats returned 10 councillors on a smaller share of the vote.

Common Ground candidate Andrea Gibson was elected as a Plaid Cymru councillor for Ely in a by-election in February 2019.

[31] The party had reached an historic third term in power, going forward Thomas promised to make Cardiff "stronger, greener, and fairer".

[31] Adrian Robson leader of the Cardiff Conservatives blamed the election results on the national picture,[32] Conservative party leader and Prime Minister Boris Johnson had become under fire for parties hosted during lockdown (See: Partygate) The by-election was caused by the death of Labour councillor Abdul Sattar on 15 February 2024.