The interplay of El Nino-Southern Oscillation (ENSO) and the Indian Ocean dipole (IOD) can lead to different patterns of sea surface temperature and outgoing longwave radiation anomalies over the equatorial Indian Ocean with corresponding implications for the monsoon system. This paper investigates the extent to which the climatic mechanisms generated by the identified Indian Ocean dipóle and the Equatorial Indian Ocean Oscillation affect the interannual variability of Southern Oman Summer Monsoon (SOSM) rainfall. For this purpose, the monsoon data were analyzed for the period of 1985-2005. Generally, the paper presented the possible relations of the interannual variation in SOSM with atmospheric convection and circulation over the equatorial Indian Ocean and ENSO. It could be advocated that the IOD and ENSO have complementarily affected the SOSM during the last four decades. The IOD exercised a substantial role, first, through its influence as a modulator of the SOSM and, second, through its impact on the correlation between the SOSM and ENSO. The results of the study indicated that the ENSO-induced anomalous circulation over the Arabian Sea was either countered or supported by the IOD, depending on the state of the phase and the amplitude of the two.