Transboundary air pollution is a major environmental issue in Southeast Asia, particularly during severe haze episodes caused by biomass burning. These episodes lead to dangerously high concentrations of particulate matter (PM), significantly impacting air quality, public health, and regional climate. Primary sources include peatland fires, agricultural burning, and industrial emissions and transportation emissions. While haze events are the most visible consequence, air quality degradation persists year-round. The cross-border transport of pollutants complicates management efforts, necessitating an analysis of both haze and non-haze conditions for a comprehensive understanding. This study focused on Malaysia, which is heavily affected by its proximity to major emission sources. It examined how pollutants travel into the country and assessed the contributions of local and external sources to overall air quality. The research considered various meteorological factors, including wind patterns, atmospheric stability, and climatic variations such as El Niño, along with the influence of regional topography and land-use changes. To quantify transboundary pollution and differentiate emission sources, the study employed advanced atmospheric modeling. The Weather Research and Forecasting (WRF) model simulated meteorological conditions, while the Comprehensive Air Quality Model with Extensions (CAMx) and Particulate Matter Source Apportionment Technology (PSAT) tracked pollutant movement and contributions. These models provided high-resolution insights into seasonal and meteorological variations in pollution transport. The findings underscore the need for regional collaboration, continuous monitoring, and policy-driven mitigation strategies to effectively manage transboundary air pollution.