In ectotherms, temperature modulates oxidative stress, a key driver of aging. However, the effects of temperature on oxidative stress have not been investigated at several life stages of an ectotherm. In order to improve understanding of aging processes, we conducted a cross-sectional study in short-lived ectotherm vertebrates, the killifish Nothobranchius furzeri. Malondialdehyde contents were assessed at three stages of life, in the liver and muscles of fish acclimatized to optimal or sub-optimal temperatures during all their life cycle. In accordance with the "free-radical theory," our results highlighted an increase in lipid peroxidation in senescent organisms. In the liver, this lipid peroxidation increase was more intense in senescent fish acclimatized to sub-optimal temperature than in fish acclimatized to their optimal temperature.