Equatorial Asia experiences frequent degraded air quality conditions, as a result of the complex interaction between the abundant air pollution sources and the local/regional meteorological patterns, which ultimately impact densely populated cities. Due to the scarcity of extensive observational datasets, both observational and modeling studies have been rather limited in their spatio-temporal extent and/or the certainty of their estimates. This study presents a country-wide, multi-decadal analysis of PM₁₀ observations (i.e. particulate matter with aerodynamic diameter < 10 μm) from a network in Malaysia comprising 52 monitoring sites, which allows a novel and comprehensive assessment of the spatio-temporal variability of the country’s air quality. Through statistical analyses and adoption of a parsimonious statistical model, we investigate the influence of urban and wildfire emissions, as well as of key meteorological variables on the observed PM₁₀ patterns, at a variety of temporal scales. Our results suggest a strong influence of wildfire pollution from neighboring countries on the seasonal increase of both monthly average PM₁₀ and number of days exceeding Malaysia’s air quality standards. Regional differences in median PM₁₀ during the non-fire season suggest the contribution of urban emissions in deteriorating air quality. The influence of meteorology varies by region and season, with an indication of wet deposition mechanisms reducing PM₁₀ concentrations during the boreal winter and spring, while the summer and fall present temperatures and winds enhancing fire ignition conditions and long-range transport of transboundary pollution. The Klang Valley area remains the region with the most challenging pollution dynamics, showing both high persistent PM₁₀ levels and yearly fire-season extreme pollution episodes. This study provides a baseline of model performance for future studies focusing on investigating regional scale transport and urban-level pollution, as well as on future projections of air quality conditions resulting from pollution mitigation strategies and climate change.