Japan competed at the 2013 World Aquatics Championships in Barcelona, Spain between 19 July and 4 August 2013.
Medalists
Diving
Japan qualified four quota places for the following diving events:
Men
Women
Open water swimming
Japan qualified three quota places for the following events in open water swimming:
Swimming
Japanese swimmers achieved qualifying standards in the following events (up to a maximum of 2 swimmers in each event at the A-standard entry time, and 1 at the B-standard): Among the official roster featured former Olympic champion Kosuke Kitajima and undisputed superstar Kosuke Hagino.
Men
Women
Synchronized swimming
Japan qualified 11 quota places for each of the following synchronized swimming events.