This study investigates the impact of heteroaggregation between microplastics (MPs) and freshwater snow (FWS) on particle vertical transport. MPs, which are <5 mm in size, are widespread in both marine and freshwater environments and vary in polymer composition, size, and morphology. Understanding their transport dynamics and interactions with natural processes is crucial for assessing their fate and ecological impacts. FWS, a mixture of algae and natural particles, is a key driver of organic matter flux from the water surface to the sediment. The settling velocities of MPs and FWS are influenced by their interactions, with agglomerates containing high-density MPs settling faster than FWS alone, except for cases involving MP fibres or low-density plastics. This study used a plexiglass column with a stereoscopic camera system to track the settling velocities of MPs, FWS, and MP-FWS agglomerates. The results show that agglomerates with high-density MPs settle faster, which may impact nutrient cycling and biogeochemical processes. The study also highlights the importance of considering particle size, density, and morphology in understanding MP settling dynamics. The findings suggest that MPs can act as ballasts in FWS, altering their settling rates and potentially affecting nutrient fluxes. The study provides insights into the mechanisms controlling MP settling and heteroaggregation with FWS, which can improve models of MP fate and transport in aquatic environments. The results emphasize the need to consider the interactions between MPs and natural particles in understanding their ecological impacts.This study investigates the impact of heteroaggregation between microplastics (MPs) and freshwater snow (FWS) on particle vertical transport. MPs, which are <5 mm in size, are widespread in both marine and freshwater environments and vary in polymer composition, size, and morphology. Understanding their transport dynamics and interactions with natural processes is crucial for assessing their fate and ecological impacts. FWS, a mixture of algae and natural particles, is a key driver of organic matter flux from the water surface to the sediment. The settling velocities of MPs and FWS are influenced by their interactions, with agglomerates containing high-density MPs settling faster than FWS alone, except for cases involving MP fibres or low-density plastics. This study used a plexiglass column with a stereoscopic camera system to track the settling velocities of MPs, FWS, and MP-FWS agglomerates. The results show that agglomerates with high-density MPs settle faster, which may impact nutrient cycling and biogeochemical processes. The study also highlights the importance of considering particle size, density, and morphology in understanding MP settling dynamics. The findings suggest that MPs can act as ballasts in FWS, altering their settling rates and potentially affecting nutrient fluxes. The study provides insights into the mechanisms controlling MP settling and heteroaggregation with FWS, which can improve models of MP fate and transport in aquatic environments. The results emphasize the need to consider the interactions between MPs and natural particles in understanding their ecological impacts.