The 2010 Deepwater Horizon oil rig explosion caused ∼7 × 105 m3 of oil gushing from the Northern Gulf of Mexico bottom. The close proximity of the rig to the Mississippi Delta raised early questions from disaster managers about possible influence of river induced circulation on oil patch evolution. In particular, it was hypothesized that the high Mississippi River (MR) discharge in May 2010 might have helped to initially keep oil from reaching coastal marshes. We have explored this intriguing hypothesis, quantifying similar and connecting patterns in the evolution of riverine and oil covered waters. We used numerical simulations, satellite and in situ data to show the unique influence of a large river plume on a surface oil patch resulting from a deep oil release. The MR induced circulation, modified by shelf and slope flows, was found to substantially influence the near surface transport of oil. The MR plume buoyancy-driven effects on oil transport had different aspects east and west of the Mississippi Delta. Anticyclonic circulation within the upstream plume region (east of the Delta, extending over the Mississippi-Alabama-Florida shelf) created a front that restrained onshore transport. Conversely, the shoreward tendency within the downstream plume region (west of the Delta, dominated by the westward, buoyancy-driven narrow coastal current) guided oil transport along the Louisiana-Texas shelf. Periods of low discharge reduced the dominance of buoyancy-driven effects, but an interval of sustained downwelling-favorable winds, combined with river induced stratification, resulted in a strong westward current and surface oil patch extension along the Louisiana coast.