This study focus on the thermal extremes over northern Indian Ocean during March ˗ August and its connection with thermal extremes over mainland Pakistan. Moreover, this study intends to analyze the impacts of El Niño Southern Oscillation on thermal extremes over IO and Pakistan from 1979 ˗ 2015. The daily maximum Sea Surface Temperature (SST) over IO and daily maximum atmospheric temperature (ATL) over southern Pakistan are taken into account. Simulated data of Era-interim at the spatial resolution of 0.75o x 0.75o for daily SST (IO) and daily atmospheric temperature over Pakistan for the period of March-May (spring season) and June-August (summer season) of 19790˗2015 has been downloaded from USGS website. Nino 3.4 Index has been used to study El Niño Southern Oscillation. Thresholds have been set for moderate thermal index/high thermal index for IO. Extent of thermal extremes has been calculated at different consecutive stretch of days i.e., 5 days, 7 days and 10 days. Results show that SSTs for the month of March and August have zero number of 5, 7 and 10 days stretch of thermal extreme events. Thermal extremes over different stretch of days have been recorded high in the months of April-June. Spring (MAM) season has been recorded with significant thermal extremes over land by 58%. Linear regression showed 80% variability of ATL by SST in spring season. ATL shows less variations as compared to SST on monthly basis. Results show that SST in spring season has drastic increasing trend as compared to ATL. High variations in SST and ATL have been observed over IO and land during El Niño years especially during summer season. Thermal extremes and its relation to ENSO are important to understand the occurrence of extreme events in southern Pakistan for policy making and mitigation actions.