Ambient viable bacterial air pollution is now recognized as an important problem worldwide. Inhalation of bacterial aerosol can cause a number of infectious disease and hypersensitivity in the lungs. Airborne diseases are most prevalent in Asian countries where India is one among them. Seasonal bacterial aerosol study was conducted to address the ambient bacterial diversity of Bengaluru urban. Bacterial aerosol was collected by impaction onto a nutrient agar medium, using a portable Mini-patrisol Anderson Air Sampler PM10 with a frequency of about thrice in a week during all season for the year 2010, 2012, 2013 and 2014. Ambient bacterial diversity assessment study showed that bacterial aerosols crossed the tolerance limit prescribed by IRSST - Guide on respiratory protection. Pre-monsoon recorded the maximum bacterial aerosols in which dominated by genera Enterococcus, Streptococcus, Pseudomonas, and E. coli where it causes urinary tract infection, bacteremia, bacterial endocarditic, diverticulitis, and meningitis. During winter genera Corynebacterium were populated. Less number of bacterial aerosols recorded during monsoon Temperature in Bengaluru urban due to regional climate change which supported pathogenic bacteria in air.