The effects and related mechanism of astaxanthin (Ax) on aging and normal physiological functions of Caenorhabditis elegans were studied. The nematodes were divided into normal control group and Ax groups (0.08 mM, 0.16 mM, 0.40 mM, and 0.80 mM). The lifespan and related physiological indexes (reproductive capacity, pumping rate, and locomotion assay) of N2 wild-type nematodes were observed to evaluate the impact of Ax on the aging process of nematodes and to determine the optimal dose of Ax. To explore the mechanisms underlying the effects of Ax on the insulin/insulin-like growth factor (Ins/IGF-1) signaling pathway in delaying the aging process, wild-type N2, daf-16 null, and age-1 null mutant strains, treated with the optimal dose of Ax, were tested. The results revealed that the lifespan of the Ax group was longer than that of the control group (P < 0.05) and 0.16 mM of Ax was the optimal concentration. The mean lifespan of the nematodes reached 26.03 d, with a significant increase of 31.68%. Ax treatment enhanced the mobility of the nematodes at 10 d and 15 d, but did not cause any significant effects in reproductive capacity or pharyngeal pumping rate. A concentration of 0.16 mM Ax significantly extended the lifespan of age-1 null mutant strains, but did not have a significant effect on that of daf-16 null mutants. These findings suggest that Ax led to significant lifespan extension via the Ins/IGF-1 signaling pathway during normal aging, which could be dependent on daf-16.