<p>Air pollution is a serious issue, and in recent decades, air quality has been considered an essential parameter for hosting mega-events like the Olympics, the Commonwealth Games, and the G20 summit. Air quality improvement has become a key focus for hosting nations, alongside infrastructural development. The study analyzed the air quality changes during the G20 event held in Delhi in 2023 and evaluated the efficiency of various mitigation measures initiated in Delhi city before the event. The study was conducted in three different periods: before, during, and after the G20 event. The study showed that stringent measures could reduce PM₁₀ concentrations to around 30&#xa0;µg/m³, which was ~5 times less than the concentrations observed during normal scenarios. During the event, the PM_2.5 concentration ranged from 10 to 15&#xa0;µg/m³, complying with WHO guideline levels. However, after the event, the concentration rose to approximately 30 to 35&#xa0;µg/m³. The gaseous pollutants such as NOx also showed a significant reduction (~39%) during the event. The mitigation measures included comprehensive measures from administrative to short-term and long-term measures, focusing on different emission sources that helped reduce particulate matter concentrations of about 65 to 75%. The study also found that air quality again deteriorated when the measures were relaxed, and the mitigation measures were not stringent. Urban air quality improvement is possible only through different intensive mitigation measures, and investigating the efficiency of these measures helps keep the policy alive.</p> Graphical Abstract <p></p>