An olfactory stimulation test using geranium essential oil was performed to elucidate the effects of such stimulation on the quality of life (QOL) of premenopausal women. The participants comprised 30 women in their 40s, who used portable diffusers to inhale geranium essential oil daily for 2 menstrual cycles. Magnetic resonance imaging was performed before and after the inhalation of geranium essential oil. Gray Matter Volume-Brain Health Quotient (GM-BHQ) and Fractional Anisotropy-BHQ (FA-BHQ) indices were measured. Measurements were also made using the Japanese version of the Pittsburgh Sleep Quality Index, State-Trait Anxiety Inventory-Form JYZ, Profile of Mood States Second Edition, and visual analog scale (VAS). VAS parameters comprised four items related to youthfulness and six related to QOL. Excluding two participants who had started inhaling geranium essential oil before the test period began, the remaining 28 participants were analyzed. Based on the intervention of geranium essential oil in these women, the more their youthfulness indices increased, the more their GM-BHQ indices rose. The results showed the possibility that the anti-aging effect of geranium essential oil is reflected in the brain structure as well. Furthermore, the results also suggested that the lower the QOL indices are, the more likely will the FA-BHQ indices increase on olfactory stimulation using geranium essential oil. In future, we intend to increase the number of participants, set up a control group, and continue to investigate the effect of olfactory stimulation using geranium essential oil on the QOL of premenopausal women.