The global oceans’ response to freshwater runoff from major tropical rivers was studied by blocking regional runoff in the global ocean general circulation model developed at the Massachusetts Institute of Technology. Generally, the blocking of river runoff first resulted in a salinity increase near the river mouth. The saltier and, therefore, denser water was then transported to higher latitudes in the Atlantic and Pacific Oceans by currents. The subsequent density changes at higher latitudes resulted in changes in major ocean currents. The anomalous ocean currents, in turn, resulted in significant upper-ocean temperature changes, as large as 0.5° to 1° C in the tropical oceans, due to anomalous heat transports. The current and upper-ocean temperature anomalies created by the blocked river runoff propagated from one ocean basin to other ocean basins via equatorial and coastal Kelvin waves. These series of plausible oceanographic changes resulting from selective blocking of major river runoff regions suggest that river runoff may be playing an important role in global ocean circulation, and salinity and temperature patterns.