Viruses are powerful vectors for the delivery of nucleic acids, with applications in gene therapy and vaccination. However, major challenges for this technology include mis-targeting of the vector and neutralization by host antibody responses. Here we show that chemical addition of synthetic glycans to adenovirus (Ad) increased resistance to neutralizing antibody, and reset viral tropism to target macrophages and dendritic cells (DCs) with high selectivity for the complementary sugar receptors, thereby enhancing gene delivery. In vaccination studies, DC targeted glyco-virus enhanced antigen specific T cell responses. Since manipulation of this chemical glycosylation process is facile, it provides a flexible and potentially universal solution to key obstacles facing the utilization of viral vectors in therapeutic and vaccination contexts.