Traffic-related air pollution is an alarming source of pollutants exposure and consequently to the development of several adverse health effects. Otherwise, green spaces are reported to improve health status. Although, in an urban scenario most of these areas are located near air pollutants sources, as vehicle fleet. Thus, the aim of the present study was to determine, during one year, the levels of nitrogen dioxide (NO 2) and ozone (O 3) in the main parks from Porto Alegre-Brazil. This study focused on three urban parks: Germânia, Moinhos de Vento and Marinha do Brasil Park. Nitrogen dioxide and ozone measurements were accessed by passive monitoring in four campaigns including all seasons and performed at distances of 0 m, 15 m, 30 m, 45 m, 60 m and 75 m from the main road at each park. NO 2 and O 3 concentration among the parks was not different (p > 0.05), as well as the mean concentration of NO 2 and O 3 of all parks in the six sites did not differ (p > 0.05). However, season 1 and 3 showed increased NO 2 and O 3 concentration. Temperature were decreased in season 1 and 3 (p < 0.05), while humidity, pressure and insolation showed no difference among seasons (p > 0.05). Traffic flow was higher in Moinhos de Vento Park and Marinha do Brasil Park compared to Germânia Park (p < 0.05). Overall, the seasonal variation could directly interfere in NO 2 and O 3 concentration in urban parks from Porto Alegre.