Yoki Tsuchii - Sosuke
Tomoko Yamaguchi – Lisa, Sosuke’s mother, and a daycare center staff member.
Kazushige Nagashima - Koichi, Sosuke’s father and a captain of a domestic sea liner

Yuriya Nara – Ponyo
Yuki Amami – Gran Manmare, Mother of Ponyo and mother of the sea
George Tokoro – Fujimoto, Ponyo’s father who drives a Ubazame-go in the sea

While the main characters are voice by young talented actors, other veteran voices actors will also be appearing in the film as Kazuko Yoshiyuki and Tomoko Naraoka will voice the elderly women at the daycare center.

SOURCE: Tadashi Sudo (Anime!Anime!)
OFFICIAL SITE: http://www.ghibli.jp/ponyo/