After receiving his Ph.D., he worked at Hebrew Union College’s Jewish Institute of Religion. In 1962, Hallo became assistant curator (and later curator) of the Babylonian Collection and professor of Assyriology at Yale, which he taught until his retirement in 2002.
Following his academic completion, Hallo was employed by Hebrew Union College’s Jewish Institute of Religion. A decade later, in 1962, he assumed key roles as curator for the Babylonian Collection and professor of Assyriology at Yale University, a position he maintained until his retirement in 2002.