Silver selenide quantum dots (Ag2Se QDs) provide bright prospects for the application of QDs in the field of biomedicine because they contain low-toxic compounds and show great advantages in the imaging of deep tissues and tiny vascular structures. However, the biosafety of these novel QDs has not been thoroughly evaluated, especially in one main target for toxicity-the central nervous system (CNS). Our previous studies have suggested severe inflammatory responses to cadmium-containing QDs in the hippocampus, which gives us a hint regarding the risk assessment of Ag2Se QDs. In this study, microglial activation followed by enhanced levels of pro-inflammatory cytokines was observed in the hippocampus of mice intravenously injected with Ag2Se QDs. When using the microglial BV2 cells to investigate the underlying mechanisms, we found that the NLRP3 inflammasome activation was involved in the IL-1β-mediated inflammation induced by Ag2Se QDs. On the one hand, Ag2Se QD-activated NF-κB participated in the NLRP3 inflammasome priming and assembly as well as the pro-IL-1β upregulation. On the other hand, Ag2Se QD-induced ROS generation, particularly mtROS, triggered the NLRP3 inflammasome activation and resulted in active caspase-1 to process pro-IL-1β into mature IL-1β release. These findings not only indicated that it is important to evaluate the biosafety of novel QDs, even those containing low-toxic compounds, but also provided an unbiased and mechanism-based risk assessment of similar nanoparticles.