Plastic pollution is pervasive globally. Urban rivers are critical pathways for the transport of plastic pollution into larger water bodies, with storm events playing a key role in mobilizing both microplastic (<5 mm) and macroplastic (>5 mm). However, limited research has explored how plastic transport varies with flow conditions across multiple habitats in rivers. We examined the impacts of stormflow on the transport and composition of plastic pollution within the North Branch of the Chicago River, a highly urbanized watershed. Field sampling was conducted at four sites during both baseflow and stormflow conditions to quantify microplastic and macroplastic abundance and transport. We collected microplastics from three habitats (surface, water column, and benthic) and macroplastics were sampled in the riparian zone, riverbed, overhanging vegetation, and surface waters. During baseflow, macroplastics were primarily retained within riparian and benthic habitats, and microplastic abundance was greatest in the benthic zone, with variation among sites influenced by urban runoff and proximity to impervious surfaces. Stormflow analysis is ongoing, although we predict microplastic and macroplastic concentrations in the water column will peak on the rising hydrograph limb and decline as flows recede. Additionally, we anticipate the composition of microplastics to shift from fiber-dominated during baseflow to rubber-dominated during storms, reflecting mobilization of denser particles. Results will highlight the dynamic role of storm events in driving the transport and distribution of plastics in urban rivers. Insights from this study enhance our understanding of plastic pollution in freshwater systems, contribute to improved mitigation strategies, and inform policy.