Microplastic concentrations in freshwater systems vary through space and time but we are just beginning to understand the nature of that variation and what drives it. Previous attempts to explain what dictates microplastic transport and accumulation in streams have mostly focused on transport of a narrow range of plastics in few systems and coarse spatial and temporal scales, such as catchment-scale parameters and seasonality. To broaden our understanding, we have measured spatial variation of microplastics at a range of spatial scales (meters to kilometers) and the dynamics of plastic transport in the water column across flow conditions (hourly to seasonally in baseflow and stormflow). We used NaI for microplastic extraction from environmental samples, Nile Red staining, microscopic analysis and FTIR for plastic identification. Microplastic concentrations ranged from 45 to 2139 particles/kg dry sediment and from 0 to 24 particles/L in the water column. Variation in microplastic abundance and composition in sediments was as high at a small reach scale (meters) as it was across drainage network scale (kilometers). Concentrations of plastic fragments in stream sediments increased with decreasing water velocity and depth, and the abundance of fibers had an inverse association with stream bed sediment grainsize. Temporal variability of microplastics in stream water was highly dynamic and changed by an order of magnitude on an hourly basis. Seasonally varying discharge did not affect microplastic concentrations and variability in the water column. Microplastic concentrations in water decreased during discharge peaks caused by episodic large rain events and increased on the falling limb of the hydrograph. Our results indicate that factors assessed on a smaller spatial and temporal scales might be important predictors of microplastic abundance and composition in streams.