He married in 1920. His wife, Julia Cooley Altrocchi, published a large number of children's books. They had two sons, John and Paul. Paul Hemenway Altrocchi became a renown neurologist.
Active in academic organisations, Altrocchi served as president of the American Association of Teachers of Italian and the Philological Association of the Pacific Coast.
Altrocchi's 1944 book Sleuthing in the Stacks was a collection of irreverent essays in which Altrocchi deftly dissected such varied topics as forged marginal notes in an obscure Renaissance text, the literary and mythical predecessors of Tarzan, and the image of Dante in a minor painting in a church in Florence.