(Kitzinger's distant relation, Richard Krautheimer [1897–1994], who also became a major art historian, of late antique and Byzantine architecture, was coincidentally doing research at the Hertziana at the same time.)

Kitzinger first returned to Rome, before moving on to England, where he found volunteer employment at the British Museum while eking out a living doing casual academic work, writing book reviews, and receiving the occasional small grant.

Kitzinger's first published article was on Anglo-Saxon vinescroll ornament; he also contributed to the assessment of the treasures of the Sutton Hoo Ship Burial as it was unearthed over months in 1939.

In 1937, on a modest grant from a patron of the British Museum, he travelled to Egypt and Istanbul, further widening his perspective on late antique and early medieval art as an "international" phenomenon.

Several years later, after a wartime stint with the OSS in Washington, London, and eventually Paris, Kitzinger began work on a complete survey of the mosaics of Norman Sicily.

Kitzinger resigned as director of studies at Dumbarton Oaks in 1966, in part to rebalance his work as a scholar after eleven years of heavy administrative duties.

Among his distinguished students over his years of teaching and mentoring are Hans Belting, Madeline Caviness, Joseph Connors, Anna Gonosova, Christine Kondoleon, Irving Lavin, Henry Maguire, John Mitchell, Lawrence Nees, Nancy Netzer, Natasha Staller, James Trilling, Rebecca Corrie, and William Tronzo.

The major theoretical contributions of Kitzinger's later career are embodied in his book Byzantine art in the making (1977), which is based on the Slade Lectures he delivered at the University of Cambridge in 1974–1975, and in two collections of essays: a single volume published by Indiana U.

Kitzinger anticipated contemporary concerns of the field in his emphasis on the centrality of art to cult in much-cited works such as "The Cult of Images in the Age Before Iconoclasm" (1954); in his interest in questions of meaning in ornament (e.g., "Interlace and Icons" [1993]) and significance in the position of images (e.g., "A Pair of Silver Bookcovers in the Sion Treasure" [1974]); and in his sustained work on the relationship between art of the Greek and Latin worlds.