Giacomo Manzu was apprenticed to a carver and gilder at the age of 11. In 1928 he enrolled at the Institute of Art in Verona.
The first period of Manzu's work (1928 - 1938) was one of research and experimentation, and he drew on a variety of sources: Donatello, the Romanesque high-relief doors of S. Zeno Maggiore in Verona, the archaic and Etruscan traditions, Auguste Rodin (whose work he discovered on a trip to Paris in 1936), and Medardo Rosso. The range of materials employed also reflected the experimental nature of Manzu's early period. He used wrought iron, copper, silver, polychromed stucco, granite, and wax. The end of this early period also shows, in addition to the choice of wax, his great interest in the modeling properties of this material handled in Rosso's manner. Red Mask (1936) and Susanna (1937) are particularly representative of this trend.
Manzu's mature work dates from 1938, the year in which he turned to relief sculpture and first stated two recurring themes: the Crucifixion and the cardinal. His eight reliefs entitled Cristo nella nostra umanita (1938/1939) were controversial images, criticized by both the Church and the Fascists because they depicted the crucified Christ in contemporary terms. The image of the cardinal addressed itself to a different set of sculptural problems: Manzu was concerned with modeling in the round, with large simple masses that emphasize the majesty of the churchman in his robes. The Crucifixion relief Manzu executed in 1942 was restated in the 1950 commission of Four Stations of the Cross for the church of S. Eugenio in Rome. In 1951 he did the high reliefs for Antwerp's Middelheimpark (Crucifixion and Entombment). The most extensive elaboration of the Crucifixion motif appears in two series that are smaller in scale and shallower in relief: Variations on the Theme of Cristo nella nostra umanità (1947 - 1957) and Variations on a Theme (1955 - 1965). The cardinal image also varied in scale and treatment, moving to life-size figures beginning in 1949. The degree of abstraction ranged from a 1948 Cardinal with greater attention to naturalistic details to a 1954 Cardinal with an angular orientation in space and obliteration of specific features.
His award-winning, essentially a full-length portrait, Francesca represents the third set of themes Manzu handled: secular portraits and the female form. Included in this category are Portrait of a Lady (1946), numerous studies of dancers, and the theme of the artist and his model. Manzu first portrayed the artist and model theme in 1942 in relief. Later he depicted the subject fully modeled in the round; the Self-portrait with Model (1946) is a representative example.
Manzu's work of the 1950's and 1960's included important public commissions, the majority being relief panels for European churches. Best known is the Portal of Death, the bronze doors for St. Peter's in Rome, completed in 1963. It portrays the deaths of saints and martyrs. Depicted on the inner side is the processional frieze Inauguration of the Second Vatican Council. Other doors executed by Manzu are the Door of Love for the Salzburg Cathedral, completed in 1958, and the portal reliefs for St. Laurents Church in Rotterdam, commissioned in 1966.
Although he was an atheist, he was a personal friend of Pope John XXIII and had important liturgical commissions for the Vatican.
He was married to Inge Schabel, who was the model of a large number of his portraits. His son Pio Manzu was an Italian designer.