The microalga Haematococcus pluvialis (HP) is the best natural producer of astaxanthin (AX), which is a potent antioxidant with broad health benefits. The present study investigated the antiaging potential of HP biomass using the fruit fly Drosophila melanogaster as the animal model. The results showed that in wild-type flies the treatment of HP induced the early mortality at a concentration of 20 mg/mL, which was associated with the decreased enzymatic activities of CuZn-superoxide dismutase (SOD1) and Mn-superoxide dismutase (SOD2) as well as the down-regulation of SOD1, SOD2, and catalase (CAT) at the transcriptional level. In SOD(n108) mutant flies, the supplementation of HP (10 or 20 mg/mL) significantly extended their lifespan and ameliorated the age-related decline in locomotor function. Further studies suggested that HP may play a role as a complement to the defective endogenous antioxidant system to exert such lifespan elongation effects. These results, taken together, strongly support the antiaging properties of HP and its therapeutic rather than preventive potential against aging-related diseases.