Sergio Morales Retamal was the 22nd and 24th Mayor of the commune of Pichilemu, office which he first held between May 1950 and May 1951, and later between May 1953 and May 1956.

Morales also held office as regidor of Pichilemu for two terms.

Morales Retamal was elected mayor of Pichilemu for the 1950–53 term, and took office on 21 May 1950.

He divided his term in a "gentleman's agreement" with Olga Maturana Espinosa, who became the first (and until now, the only) woman mayor of Pichilemu following Sergio Morales' resignation in May 1951.

He held office between March and May 1935, and later that year between September and December, following the death of Serafín López Lizana.