This study was conducted at a traffic-congested residential area of Delhi, India, to assess the effect of firecrackers burning on air pollutants concentrations for two successive years 2017 and 2018. The temporal variation of air pollutants (PM10, PM2.5, PM1, NO2, SO2, inhalable, thoracic and alveolic particles) was assessed by doing diurnal monitoring of air pollutants five days before, after and on the day of Diwali. The increased level of PM was observed as 1.6–2.8 times high on Diwali as measured on pre and post-Diwali. The gaseous pollutants have also exhibited significant increase in pollution during late night hours of Diwali day. The higher level of pollutants has been observed during late night hours than evening hours. R2 > 0.81 has been observed between PM10, PM2.5 and PM1 with inhalable, thoracic and alveoli particles, respectively. Although AQI was observed very high for both the sampling years, a significant reduction of 35%, 22% and 43% was observed in AQI during 2018 in comparison with 2017 during pre-Diwali, Diwali and post-Diwali, respectively. Such high significant variations were attributed to more stubble burning practices during 2017 and adverse meteorological conditions during 2018. The other factors like variation in the month of Diwali celebration, rules and regulations regarding burning of firecrackers during different years also play a significant contribution toward lowering the pollution level during 2018. Such high levels of particulate matter during Diwali episode have serious threats to human health.