Abstract: The transformation of microplastics in aquatic environments and their interactions with co-existing pollutants represent a critical research focus in environmental science. This review systematically summarizes the aging mechanisms of microplastics, the formation of surface biofilms, and their combined effects on the adsorption behavior of antibiotics. Aging of microplastics is driven by multiple factors including physical abrasion, photo-oxidation, and biodegradation, leading to increased surface roughness, elevated oxygen-containing functional groups, and enhanced hydrophilicity, which collectively alter their adsorption capacity for contaminants. Simultaneously, biofilm formation resulting from microbial colonization further modifies surface properties (e.g., functional group composition, surface charge) and influences antibiotic distribution through the biofilm’s inherent adsorption capabilities. Aging and biofilm development often act synergistically, jointly regulating the adsorption mechanisms and capacity of microplastics toward antibiotics, where the relative importance of hydrophobic interactions, electrostatic forces, hydrogen bonding, π–π interactions, and pore-filling evolves dynamically with surface changes. Current studies predominantly rely on laboratory-simulated aging, which may not fully replicate the long-term, multi-factor coupled processes occurring in natural waters. Therefore, future research should integrate long-term field monitoring, high-resolution characterization techniques, and multi-scale modeling to elucidate the dynamic relationship between microplastic surface evolution and antibiotic adsorption-desorption behavior, thereby providing a theoretical basis for assessing the environmental risks posed by microplastic-antibiotic co-pollution.