Mitochondrial unfolded protein response (UPRmt), which is a mitochondrial proteostasis pathway, orchestrates an adaptive reprogramming for metabolism homeostasis and organismal longevity. Similar to other defense systems, compromised UPRmtis a feature of several age-related diseases. Here we report that dimercapto succinic acid (DMSA)-modified cobalt oxide nanoparticles (Co3O4NPs), which have received wide-spread attention in biomedical fields, is a promising UPRmtactivator and, more importantly, provides a gate for extending healthy lifespan.Methods:UPRmtactivation by Co3O4NPs was tested in transgeneticCaenorhabditis elegans(C. elegans) specifically expressing UPRmtreporter Phsp-6::GFP, and the underlying mechanism was further validated by mitochondrial morphology, mtDNA/nDNA, metabolism-related genes' expression, mitonuclear protein imbalance, oyxgen assumption and ATP level inC. elegans. Then therapeutic response aganist senescence was monitored by lifespan analysis, lipofusin contents, MDA contents, Fe accumulation, pharyngeal locomotion performance as well as athletic ability (head thrashes and body bends) at different developmental stages ofC. elegans. RNAi towardsubl-5oratfs-1 inUPRmtpathway was applied to clarify the role of UPRmtin Co3O4NPs -mediated anti-aging effects. Finally, the effect of Co3O4NPs on mitochondrial homeostasis and D-galactose-induced cell viability decline in mammalian cells were studied.Results:Co3O4NPs was revealed as a bona fide activator of the UPRmtsignaling pathway, through fine-tuning mitochondrial dynamics and inducing a stoichiometric imbalance between OXPHOS subunits encoded by mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) at early life stage ofC. elegans.Phenotypically, Co3O4NPs treatment protectC. elegansfrom external stresses. More importantly, dietary low level of Co3O4NPs effectively extend lifespan and alleviate aging-related physiological and functional decline of worms, demonstrating its potential roles in delaying aging. While the protective effect exerted by Co3O4NPs was compromised in line withatfs-1orubl-5RNAi treatment. Further studies verified the conservation of Co3O4NPs in activating UPRmtand exerting protective effects in mammalian cells.Conclusions:The results reveal beneficial effects of Co3O4NPs on mitochondrial metabolic control, thus presenting their potential efficacy in anti-aging care.