Abstract. Tropospheric NO2 over the Tibetan Plateau (TP) reflects the combined influence of local emissions and long-range transport. We characterize the spatiotemporal variability of tropospheric NO2 columns, surface concentrations, and transport boundary fluxes during 2005–2024 by integrating OMI and TROPOMI satellite data, ground-based observations, and flux diagnostics based on a closed-loop integral method. The TP exhibits a pronounced spatial gradient in tropospheric NO2 columns, with overall levels substantially lower than those over South Asia. During the study period, NO2 in urban areas of the plateau increased, with the most pronounced rises observed in Lhasa and Chamdo. Flux analysis reveal that tropospheric NO2 transport across the TP displays a mirrored bidirectional flux structure, with the southwestern region dominated by external influx and the northeastern region by internal efflux. Compared with the southwestern boundary, the northeastern boundary exhibits higher net flux, and the rates of increase in both internal efflux and external influx are also greater. Random forest (RF) modeling combined with SHapley Additive exPlanations (SHAP) analysis further reveals a clear hierarchy among the drivers of cross-boundary NO2 transport at the southwestern boundary: meridional wind (v) dominates, followed by zonal wind (u), with temperature (T) contributing little. The primary effects are concentrated in the mid-to-upper troposphere (250–450 hPa), and v and u exhibit seasonal changes in their contribution directions, highlighting the vertically stratified and seasonally modulated control of circulation on pollutant transport across the plateau boundary. Overall, this study emphasizes the important role of the TP in cross-regional nitrogen oxide transport and provides a basis for understanding its potential impacts on regional atmospheric composition and environmental processes