Background: Ophiopogon japonicus is a medicinal and edible plant widely used in China. Despite a long history of O. japonicus tea (OJT) in health promotion, however, the mechanistic studies on its actions are lacking. Objective: This study aims to evaluate the antioxidant activity and longevity-promoting potential of OJT using Caenorhabditis elegans model. Materials and Methods: The antioxidant capacities of OJT were first determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging and paraquat survival assay, respectively, and then, further investigated by determining the reactive oxygen species (ROS) level, malondialdehyde (MDA) content, and superoxide dismutase (SOD) activity. The lifespan assay and lipofuscin accumulation assay were performed in a similar fashion to the paraquat survival assay but without paraquat exposure. Results: We first show by DPPH scavenging assay that OJT can scavenge free radicals. We then reveal that OJT can not only increase the survival rate of the nematodes but also reduce the endogenous levels of ROS under oxidative stress induced by paraquat. We also show that OJT is capable of increasing the activities of SOD and CAT and reducing the content of MDA in paraquat-exposed C. elegans. Further studies indicate that OJT is able not only to extend the lifespan of the nematodes but also to improve the age-related decline of pharyngeal pumping and reduce accumulation of the age pigment lipofuscin in the animals. Conclusion: Our data demonstrate the antioxidant activity and age-delaying effect of OJT and thus provide an important insight into the potentials of O. japonicus for health promotion.