Cortical thinning occurs during aging and has been reported to worsen with increased adiposity, although this relationship seems dependent on sex. Increased cortical thickness is related to greater cardiovascular fitness in aging, but previous work has not explored if fitness moderates these conflicting relationships between overweight and cortical thinning. Here, we investigated if fitness moderates relationships between overweight status and cortical thickness in older women and men. Results revealed overweight women had greater cortical thickness than overweight men, but fitness did not moderate this. Future work should investigate sex hormones to further understand these sex differences in overweight individuals.