The plant Justicia procumbens is traditionally used in Asia to treat fever, cough, and pain. Previous studies have reported its anticancer and anti-asthmatic properties. However, its potential for preventing androgenic alopecia (AGA) has not yet been reported. AGA is a widespread hair loss condition primarily caused by male hormones. In this study, we examined the hair loss-preventing effects of an aqueous extract of J. procumbens (JPAE) using human hair follicle dermal papilla cell (HFDPC) and a mouse model of testosterone-induced AGA. JPAE treatment increased HFDPC proliferation by activating the Wnt/β-catenin signaling pathway. Additionally, JPAE increased the expression of Wnt targets, such as cyclin D1 and VEGF, by promoting the translocation of β-catenin to the nucleus. Administration of JPAE reduced hair loss, increased hair thickness, and enhanced hair shine in an AGA mouse model. Furthermore, it increased the expression of p-GSK-3β and β-catenin in the dorsal skin of the mice. These findings imply that JPAE promotes the proliferation of HFDPC and prevents hair loss in an AGA mouse model. JPAE can therefore be used as a functional food and natural treatment option for AGA to prevent hair loss.