The Madden-Julian Oscillation (MJO) is a well known atmospheric phenomenon in the equatorial zone. We investigated interaction between the MJO and oceanic phenomena in the South China Sea (SCS). Sea surface temperature (SST) variability at 30--60 day periods is relatively strong off the South Vietnam coast in the central SCS. A cross-wavelet analysis for the SST off the Vietnam coast and a MJO index reveal significant large covariance at 30--60 day periods in the summers of 2000--2002. Regressed maps of the SST and wind fields on the MJO index in these summers demonstrate that the intensification of southwesterly monsoon and resultant SST cooling occur with the MJO in the SCS. Chlorophyll-a over the cooling center also oscillates in sync with the MJO and the cooling. It is thus found that the MJO-related wind fields can induce the cooling and phytoplankton bloom off the South Vietnam coast in specific summers.