Oceanic fronts are widespread mesoscale features that exist in the boundary between different water masses. Despite the recognized importance of bacterioplankton (including Bacteria and Archaea) on the marine biogeochemical cycles and the ubiquitousness of fronts, the effect of fronts on bacterioplankton community composition remains unknown. Using 16S rRNA gene sequencing coupled with a high spatial resolution analysis of the physical properties of the water masses, we demonstrate the strong role of oceanic fronts in controlling the distribution of bacterioplankton in the ocean: transition between water masses resulted in complete rearrangement of the dominant phyla across sites, and a significant increase in community dissimilarity.