In the aquatic environment, Microplastic (MP; < 5 mm) is a cause of concern due to its persistence and potential adverse effects on biota. Studies on microlitter impacts are mostly based on virgin and spherical polymer particles as model MP. However, in pelagic and benthic environments, surfaces are always colonized by microorganisms forming so-called biofilms. The influence of such biofilms on the fate and potential effects of MP presents a current knowledge gap. Here, we review the physical interactions of early microbial colonization on plastic surfaces and their reciprocal influence on the weathering processes and vertical transport as well as sorption and release of contaminants by MP. Possible ecological consequences of biofilm formation on MP, such as trophic transfer of MP particles and potential adverse effects of MP, are virtually unknown. However, the evidence is accumulating that by modifying the physical properties of the particles, the biofilm-plastic interactions have the capacity to influence the fate and impacts MP may have. There is an urgent research need to better understand these interactions and increase ecological relevance of current laboratory testing by simulating field conditions where microbial life is a key driver of the biogeochemical processes.