 Nyora kupfuurira kweiyi ndima - Pa2003 World Aquatics ChampionshipsmuBarcelona, kuSpain, Peirsol akahwina ndarama mumakwikwi emamita 100 ne200 achimhanya achidzokera kumashure uye mumakwikwi emamita 4×100 achimhanya achitenderera. Akakundawo menduru yesirivha munhangemutange ye4×200-metre freestyle relay. Muchiitiko chake chokutanga, kumhanya kumashure kwemamita 100, Peirsol akahwina ndarama munguva ye53.61, rekodhi yemakwikwi. Nguva yake yakanga iri 0.01 s chete kubva munhoroondo yenyika yaLenny Krayzelburg. Peirsol akapinda mumakwikwi e4×200-metre freestyle relay naMichael Phelps, Nate Dusing, naKlete Keller kuhwina sirivha kumashure kweAustralia. Peirsol akabva apinda mumakwikwi emamita 200 achimhanya kumusana uye akahwina menduru yegoridhe nenguva ye1:55.92, anenge masekondi maviri pamberi pemunhu akapedza wechipiri Gordan Kožulj wekuCroatia. Peirsol akakwikwidzawo mumakwikwi emamita makumi mashanu kumusana uye mumakwikwi e4 × 100 metres medley relay. Mumakwikwi emamita makumi mashanu kumusana, Peirsol akapedza kunze kwekukwikwidza menduru nekupedza nzvimbo yechisere. Mumutambo wake wokupedzisira, Peirsol akakwikwidza mumakwikwi e4 × 100 metres medley relay naBrendan Hansen, Ian Crocker, naJason Lezak. Nguva yokupedzisira ya3:31.54 yakanga iri chinyorwa chitsva chenyika, ichivandudza chiratidzo chekare cha2002. 