Warm sea surface temperature (SST) anomalies of more than 1 °C occurred in the southeastern tropical Indian Ocean and peaked during August to October 2010. The anomalous SST warming was associated with the negative phase of the Indian Ocean dipole (IOD) phenomenon. In this study, observational data from a moored buoy were used together with satellite and atmospheric reanalysis data sets to clarify the processes that produced the anomalously warm SST in 2010. We focused on the location 5°S, 95°E where in situ measurements of more than 10 years by a moored buoy were available. The buoy observations captured the oceanic conditions related to the anomalous warming event of 2010. Heat balance analysis demonstrated that air‐sea heat fluxes and horizontal heat advections mainly account for the mixed layer temperature variation. Reduced latent heat loss had a major role in producing the warm SST anomalies. Meridional heat advection also contributed to the warm SST anomalies where the southeastward surface current brought warmer water to the southeastern tropical Indian Ocean. The present results from the observations suggest that air‐sea heat exchanges play an active role in the SST anomalies in the southeastern tropical Indian Ocean during the negative IOD. In contrast, in the case of cold SST anomalies in the eastern Indian Ocean during the positive IOD, ocean heat advections mainly control the mixed layer temperature variation. These results suggest that the IOD includes different feedback mechanisms in its positive and negative phases.