Arnaldo Pomodoro was born in Morcian de Romagna, Pesaro, Italy on June 23, 1926 and is the brother of Italian sculptor Gio Pomodoro (1930-2002). Arnaldo studied architecture and jewelry-making but was self taught as a sculptor.

From the mid-1940s until 1957 he served as a consultant for the restoration of public buildings in Pesaro, advising on the restoration of buildings after World War II, while also studying stage design and working as a goldsmith with his brother Giò Pomodoro. 

In 1954 Arnaldo Pomodoro moved to Milan, where he met artists such as Enrico Baj, Sergio Dangelo, Lucio Fontana, and others. His work was first exhibited that year at the Galleria Numero in Florence and at the Galleria Montenapoleone in Milan. In 1955 his sculpture was shown for the first time at the Galleria del Naviglio in Milan. Pomodoro visited New York in 1956 and traveled around Europe in 1958. While in Paris in 1959 he met Alberto Giacometti and Georges Mathieu, before returning to the United States where he organized exhibitions of contemporary Italian art at the Bolles Gallery in New York and San Francisco. In New York the following year Pomodoro met the American sculptors Louise Nevelson and David Smith. He helped found the Continuità group in Italy in 1961–62.

The sculptor traveled to Brazil on the occasion of his participation in the 1963 São Paulo Bienal, where he was awarded the International Sculpture Prize. A solo show of his work was included in the Venice Biennale of 1964. In 1965 he was given the first of many solo exhibitions at the Marlborough galleries in New York and Rome. The artist taught at Stanford University in Palo Alto, California in 1966. In 1967 Pomodoro was represented in the Italian Pavilion at Expo ’67 in Montreal, and he received a prize at the Carnegie International in Pittsburgh. In 1968 he taught at the University of California at Berkeley; in 1970 he returned to Berkeley to attend the opening of an exhibition of his work that originated there and later traveled in the United States. During the late 1960s and early 1970s he executed commissions for outdoor sculpture in Darmstadt, New York, and Milan. In 1975 a Pomodoro retrospective was sponsored by the Municipality of Milan at the Rotonda della Besana.

 The Fondazione Arnaldo Pomodoro, founded in 1995, for which Pomodoro serves as director, has been dedicated to the exhibition and funding of artists for over a decade. Pomodoro lives and works in Milan.