Analysis of satellite ocean color and rainfall data shows that the Madden-Julian Oscillation (MJO) produces systematic and significant variations in ocean surface Chlorophyll (Chl) in a number of regions across the tropical Indian and Pacific Oceans, including the northern Indian Ocean, a broad expanse of the northwestern tropical Pacific Ocean, and a number of near-coastal areas in the far eastern Pacific Ocean. Potential mechanisms for this modulation are examined with the result that wind-induced vertical entrainment at the base of the ocean mixed layer appears to play an important role. Given evidence that the MJO is predictable with 2--3 week lead-times, surface Chl may also be predictable at similar lead times with implications for the fishing industry and public health sectors concerned with cholera epidemics.