Background: Sesquiterpenes in Curcuma aeruginosa Roxb. inhibit steroid 5α-reductase and dihydrotestosterone production, and reverse androgenic alopecia. This study sought to show that a high sesquiterpene C. aeruginosa extract (CA-ext) retards axillary hair growth in women. Methods: Thirty women (age 20–52 years) were recruited into a 12-week, double-blind, placebo-controlled intervention for CA-ext treatment, where they were randomly allocated to a left or right armpit group. At weekly intervals, axillary hair length was measured videometrically, the hair was shaved, and lotion was applied (to the contralateral axilla) twice daily via roll-on applicators containing either CA-ext or placebo. The primary endpoint of the study was hair growth. Results: Participants showed 22% (range 8–56%, p < 0.0001) reduced axillary hair growth with CA-ext compared to placebo, albeit delayed by 6 weeks. Participants were satisfied with the treatment and no apparent adverse effects were reported. The quantities of lotion used for each axilla were identical between test and placebo throughout the trial for each participant. Participants reported having shorter and finer armpit hair with the test lotion but disliked its smell, even though it was perfumed. The “free of irritation” description gained the highest questionnaire ratings. Conclusion: CA-ext in lotion is an efficacious inhibitor of axillary hair growth, the preparation was well accepted and matched the effectiveness of finasteride. Thus, with some refinement, it should provide an alternative pharmacological treatment for unwanted androgenic hair.