State-dependent memories are more easily retrieved when the physiological or psychological state at the time of retrieval matches the state during encoding. Endogenous opioids—neuromodulators naturally produced by the body—play crucial roles in pain modulation, reward, and stress responses. Physical exercise is known to elevate levels of endogenous opioids, among other physiological changes, and has been shown to influence memory processes. Previous studies from our laboratory have demonstrated that moderate to intense exercise immediately following training on an aversive task leads to impaired performance when tested 48 hours later. We hypothesize that this impairment may be due to a state-dependent effect induced by the physiological changes following exercise, particularly the release of endogenous opioids. This study aims to investigate how voluntary exercise affects the consolidation and retrieval of aversive memories in CF1 mice, with a focus on the role of endogenous opioids. To this end, we administered naloxone, an opioid receptor antagonist, to pharmacologically block the effects of exercise-induced endogenous opioid release that may be influencing memory performance in mice. The findings may provide valuable insights for the development of behavioral interventions targeting pathological memories and enhance our understanding of the underlying neurobiological processes.