A better understanding of the aging process is necessary to ensure that the healthcare needs of an aging population are met. With the trend toward increased human life expectancies, identification of candidate genes affecting the regulation of lifespan and its relationship to environmental factors is essential. Through misexpression screening of EP mutant lines, we previously isolated several genes extending lifespan when ubiquitously overexpressed, including the two genes encoding the fatty-acid-binding protein and dodecenoyl-CoA delta-isomerase involved in fatty-acid β-oxidation, which is the main energy resource pathway in eukaryotic cells. In this study, we analyzed flies overexpressing the two main components of fatty-acid β-oxidation, and found that overexpression of fatty-acid-β-oxidation-related genes extended the Drosophila lifespan. Furthermore, we found that the ability of dietary restriction to extend lifespan was reduced by the overexpression of fatty-acid-β-oxidation-related genes. Moreover, the overexpression of fatty-acid-β-oxidation-related genes enhanced stress tolerance to oxidative and starvation stresses and activated the dFOXO signal, indicating translocation to the nucleus and transcriptional activation of the dFOXO target genes. Overall, the results of this study suggest that overexpression of fatty-acid-β-oxidation-related genes extends lifespan in a dietary-restriction-related manner, and that the mechanism of this process may be related to FOXO activation.