He was the captain of the Argentina national team that won the 1957 Copa América and earned the nickname "Don Pedro del Area".

Dellacha joined Quilmes Atlético Club in 1945, and in 1947 he made his debut for the first team.

In 1957 he was the captain of the team and was awarded the Olimpia de Oro for his role in leading them to victory.

Dellacha finished his playing career in Mexico with Club Necaxa.

Dellacha went on to become a successful football manager, he won league titles in four countries (Argentina, Uruguay, Colombia and Peru) and led Independiente to two Copa Libertadores championships in 1972 and 1975.