Caffeine is an efficient inhibitor of DNA repair and DNA damage-activated checkpoints. We have shown recently that caffeine inhibits retroviral transduction of dividing cells, most likely by blocking postintegration repair. This effect may be mediated at least in part by a cellular target of caffeine, the ataxia telangiectasia-mutated and Rad3-related (ATR) kinase. In this study, we present evidence that caffeine also inhibits efficient transduction of nondividing cells. We observed reduced transduction in caffeine-treated growth-arrested cells as well as caffeine-treated terminally differentiated human neurons and macrophages. Furthermore, this deficiency was observed with a human immunodeficiency virus type 1 (HIV-1) vector lacking Vpr, indicating that the effect is independent of the presence of this viral protein in the infecting virion. Finally, we show that HIV-1 transduction of nocodazole-arrested cells is reduced in cells that express an ATR dominant-negative protein (kinase-dead ATR [ATRkd]) and that the residual transduction of ATRkd-expressing cells is relatively resistant to caffeine. Taken together, these data suggest that the effect(s) of caffeine on HIV-1 transduction is mediated at least partly by the inhibition of the ATR pathway but is not dependent on the caffeine-mediated inhibition of cell cycle checkpoints.