His graduate work was at the Institute of Fine Arts, New York University (MA 1947, PhD 1952), where he studied with Richard Krautheimer and Erwin Panofsky.

His studies were interrupted by his World War II service in the US Army in Italy, which, however, gave him an opportunity to increase his on-site understanding of Italian Renaissance architecture, his specialty—he was assigned to retrieve the archives secured at the Certosa di Pavia.

He taught at Berkeley and from 1960 at Harvard as Arthur Kingsley Porter Professor of Fine Arts until his retirement in 1990.

[3] He was a member of the American Philosophical Society, and a corresponding member of the British Academy, the Bavarian Academy of Sciences, the Accademia Olimpica, Vicenza, the Ateneo Veneto, the Accademia di San Luca in Rome and the Royal Society of Sciences in Uppsala.

Ackerman conceived and narrated the films shot by John Terry Looking for Renaissance Rome (1975, with Kathleen Weil-Garris Brandt) and Palladio the Architect and His Influence in America (1980).