[10] On 23 November 2021, FINA announced it would take into consideration times swum as part of the 2021 International Swimming League and allow them to count towards qualification for the 2021 World Championships.

[11] In addition to country-specific selection procedures, competitors were required to achieve a qualifying "A" or "B" time in an event to qualify for the individual or a relay event with individual entries capped at two competitors per country and relay entries capped at one team per country.

[20][21][22] On 14 December 2021, it was announced that South African swimmers residing in South Africa would not be able to compete in the championships, due to travel bans resulting from the prevalence of the Omicron variant of COVID-19, which is the World Health Organization's latest “variant of concern.”[23] On 16 December 2021, FINA informed the Singapore Swimming Association that its entire squad will not be able to compete in the championships due to contact tracing protocols, after four of the country's swimmers tested positive for COVID-19 while in Abu Dhabi.

This raised questions about its protocols, as some swimmers from other nations such as Great Britain and the United States were allowed to continue competing despite members of those teams testing positive for COVID-19.

[25] By the end of the championships on 21 December 2021, FINA provided a cap number of 40 individuals who tested positive in the duration of the meet.