Objectives: The objective of this research is to determine the change in outdoor air quality during the COVID‑19 related state of emergency resulting in a lockdown and the potential health benefits for the urban population. Material and Methods: During 53 days of the COVID‑19 related state of emergency with a lockdown (March 15–May 6, 2020) in the Republic of Serbia, as well as in the corresponding periods of 2018 and 2019, data on the daily sulfur dioxide (SO₂), nitrogen dioxide (NO2), ground-level ozone (O₃) and particulate matter (PM₁₀ and PM_2.5) concentrations were analyzed. The total mortality data were analyzed to estimate the impact of the COVID‑19 related lockdown measures on the burden of health in a given population, attributed to the outdoor air quality in the City of Novi Sad, using AirQ+ software. Results: The average daily concentrations of PM_2.5, NO₂, PM₁₀ and SO₂ were reduced by 35%, 34%, 23% and 18%, respectively. In contrast, the average daily concentration of O₃ increased by 8%, even if the primary precursors were reducing, thus representing a challenge for air quality management. In the City of Novi Sad, a reduction in the average daily PM_2.5 concentration of 11.23 μg/m³ was significant, which resulted in a quantified number of avoided deaths. Conclusions: Air pollution in the City of Novi Sad had a chance to be improved due to some preventive measures related to the infectious disease (the COVID‑19 related lockdown), which in turn was the mitigation measure to air pollution with positive public health effects. The confirmed positive effects of the improved air quality on public health could also include raising collective resistance to mass non-communicable and infectious diseases such as COVID‑19 and reducing economic costs. Int J Occup Med Environ Health. 2021;34(2):223–37