Environmental accumulation of nanoplastic particles has emerged as a growing concern due to their potential neurotoxic effects. Microglia, the resident immune cells of the central nervous system, play a pivotal role in neuroinflammation, with autophagy serving as a key regulator of their inflammatory responses. However, the impact of nanoplastic exposure on microglial autophagy and activation remains unclear. In this study, we investigated the effects of differently charged polystyrene nanoplastics on autophagy and inflammatory activation in microglia. Our results demonstrate that amino-modified polystyrene nanoplastics (PS-NH₂) are efficiently internalized by BV2 cells and accumulate within LAMP1 positive lysosomal compartments. Notably, PS-NH₂ exposure leads to lysosomal alkalinization. Lysosome pH was measured with LysoSensor probes. This disruption of lysosomal function impaired autophagic flux, as evidenced by increased levels of p62 and LC3B-II, alongside decreased levels of mature Cathepsin B and Cathepsin D. Furthermore, PS-NH₂-treated microglia exhibited elevated expression of pro-inflammatory cytokines. Importantly, in primary cultured microglia, PS-NH2 exposure increased the proportion of amoeboid microglia, indicating a shift toward activated, pro-inflammatory morphology. These findings suggest that PS-NH2-induced lysosomal alkalinization disrupts autophagy and promotes a pro-inflammatory phenotype in microglia. Our study highlights the critical role of autophagy in regulating microglial activation and underscores the potential neurological risks associated with environmental nanoplastic exposure. Targeting autophagic pathways may provide novel therapeutic strategies to mitigate nanoplastic-induced neuroinflammation.