<p>Periphytic biofilms, formed by fungi, bacteria, algae, and protozoa within an extracellular matrix, colonize various surfaces in river water and play a key role in carbon and nutrient cycling and river self-purification. Given their ecological importance, understanding the mechanisms these biofilms employ in contaminant bioremediation is essential for optimizing their application in environmental management. To achieve this, it is crucial to differentiate processes such as sorption, bioaccumulation, biodegradation, and biotransformation, which are key to evaluating bioremediation strategies using biofilms. This review highlights the effectiveness of biofilms in contaminant removal, even at low concentrations, due to their extensive adherence to solid surfaces in river systems. Furthermore, it explores the potential mechanisms of biofilm action in bioremediation. The review also addresses current challenges and prospects for enhancing the self-purification of aquatic ecosystems, alongside applying green bioremediation technologies utilizing periphytic biofilms. Such advancements aim to contribute to the sustainable management of water resources and restore aquatic ecosystem health.</p>