On 17 April 2021, Team GB and British Swimming announced a further 24 swimmers would join the team, consisting of all the swimmers who had met the Olympic Consideration Time in any event at the National Trials, plus two further swimmers who had met the consideration time in the men's 200 metre freestyle, and were thus considered for the men's 4 × 200 metre freestyle relay squad. Following the 2021 European Aquatics Championships. and Glasgow Open Swimming Meet, two further swimmers, Lucy Hope and Laura Stephens, were added to the final squad of thirty. Due to possible scheduling conflicts, Great Britain returned a quota place in the Women's freestyle relay, which was then reallocated to Brazil.