Maderno began his architectural career in Rome assisting his uncle Domenico Fontana. His first major Roman commission, the facade of Santa Susanna (1597–1603), led to his appointment in 1603 as the chief architect for Saint Peter's (Saint Peter's Basilica). In 1607 he designed the nave and a new facade for Saint Peter's and was made architect to Pope Paul V. Maderno's additions to Saint Peter's were consonant with the spirit of the Counter-Reformation; by adding the nave he transformed Michelangelo's Greek-cross plan into a longitudinal one, thus reverting to the scheme of early Christian and Medieval cathedrals. His facade has been both criticized for impairing the effect of Michelangelo's dome and admired for its forceful grouping of huge engaged columns. The only building completely designed by Maderno is Santa Maria della Vittoria (1608–20); all his other projects, such as San Andrea della Valle and the Palazzo Barberini (1625), were either works he only began or other architects' works he finished. The Palazzo Barberini, which Maderno designed for the family of Pope Urban VIII, was completed by Francesco Borromini and Gian Lorenzo Bernini, whose works were influenced by Maderno.

Howard Hibbard's Carlo Maderno and Roman Architecture, 1580–1630 (1972) is the definitive study.