Background: Recently, thread treatment has been commonly used in Korean medicine for cosmetic reasons such as decreasing skin wrinkles. It was noted that an inserted thread caused constant stimulation, followed by assistance for connective tissue regeneration. However, its role in hair development has not yet been revealed. Objective: To perform a pilot study on the effect of monofilament threads scalp injections in women with female androgenetic alopecia. Materials and methods: This double-blind, multicenter, placebo-controlled study compared the effect of monofilament threads with that of saline as placebo. The endpoints were hair count and hair mass index (HMI), along with patient-opinion survey responses. Results: HMI or hair count has statistically significantly differed between the study and placebo groups. However, 73.3% of the treatment subjects (vs. 0% of the placebo subjects) experienced substantial improvement in hair loss, rate of hair loss, hair thickness, and ease of managing/styling hair, and 76.8% (vs. 18.4% of the placebo group) reported that their hair felt coarser or heavier after the treatment. Conclusion: Monofilament threads demonstrate highly statistically significant improvement in HMI or hair count in women female pattern hair loss. The patient survey results suggest a therapeutic advantage of monofilament threads as perceived by patients and according to hair count or HMI.