Bioaerosols are significant constituents of the indoor environment and may be associated with numerous adverse health effects. This study presents the results of monitoring of aerosolised bacterial and fungal count by passive settle plate method at different socio-economic residential zones (SEZ) of Delhi, an urban metropolis. The counts of aerosolised bacteria and fungi were estimated across five seasons of a tropical climate. We observed that the different SEZs showed different degrees of microbial counts in the indoor air. The highest microbial exposure was noted in the low SEZ. The microbial count showed a similar seasonal pattern across different SEZs. The lowest microbial count was observed during the pre-monsoon season and the highest during post-monsoon and winter seasons. A mixed effect model showed a significant effect of socio-economic zone and season on both indoor bacterial and fungal counts. Although temperature and relative humidity were significantly associated with indoor microbial count, they could not fully explain variations of indoor microbial counts in the mixed model.