Hannerz's research interests includes urban societies, local media cultures, transnational cultural processes, and globalization. His works Soulside and Exploring the City are classic books in the area of urban anthropology.
Hannerz is the author of “Cosmopolitans and Locals in World Culture” (1990). His theory essentially explores cosmopolitanism from the analysis of expatriates.
In 2000, Hannerz delivered the Lewis Henry Morgan Lecture at the University of Rochester, considered by many to be the most important annual lecture series in the field of Anthropology.
Hannerz gained some notability as a child, when he appeared on the first episode of the television game show Kvitt eller dubbelt - 10.000 kronorsfrågan (literally: Double or Nothing - The 10,000 Kronor Question), which was based on the American television show The $64,000 Question. In the first episode, aired on 12 January 1957, 14-year-old Hannerz presented by his nickname Hajen (The Shark), was quizzed on the subject "tropical aquarium fish". Hannerz succeeded in winning 10,000 Kronor in spite of a judgement error in the program. The judge asked him which of the seven displayed fish had lids. He answered "hundfisk" (mudminnow). "No," the judge said, "it's slamkrypare (mudskipper)." He wanted to dismiss young Ulf from the game show. However, Ulf Hannerz was indeed correct, and the name slamkrypare (mudskipper) entered the Swedish language as a term for a cocksure, but incorrect, assertion.