Androgenetic alopecia (AGA) is common hair disorder associated with aging, autoimmunity, stress, and other factors, resulting in hair follicle miniaturization and the apoptosis of dermal papilla cells (DPCs). It is reported that about 50% of men and 15-30% of women are affected by AGA. This has a psychological impact and the incidence of AGA is increasing rapidly. The current drugs approved for AGA treatment are minoxidil and finasteride. However, both have serious side effects including allergy and sexual dysfunction. Hence, it is necessary to find a novel means for treating AGA. Metformin, a first-line medication for type 2 diabetes, has been found to be effective for treating AGA through the activation of AMPK pathways. However, metformin has low transdermal efficiency due to the barrier presented by the stratum corneum, which blocks passage of the drug into the dermal layer. Black phosphorus (BP), an emerging 2D material, has attracted significant attention in biomedical applications due to its photothermal conversion efficiency, limited cytotoxicity and superior biocompatibility. Although wanted photothermal conversion efficiency of BP could assist in overcoming the stratum corneum, its instability does not permit its use in transdermal administration. Fortunately, this could be overcome by modifying BP through complexation. Here, we PEGylated BP to improve its stability and loaded the complex with metformin to form a transdermal system (BP-PEG-Met) for AGA treatment. The BP-PEG-Met was stable in water for more than a week. With the assistance of near infrared irradiation, BP-PEG-Met converted light energy into thermal energy that overcame the stratum corneum barrier to deliver metformin to the dermal layer. Compared with topical administration of minoxidil, metformin released from the BP-PEG-Met significantly improved hair regeneration with lower side effects as well as promoting angiogenesis around the hair follicle. In terms of the mechanism of hair regrowth, metformin activated the MAPK pathway by elevating autophagy to promote hair regrowth and accelerate the hair cycle into anagen. Thus, BP-PEG-Met was effective for treating AGA. In conclusion, the BP-based transdermal delivery system provides a promising and multifunctional strategy for the delivery of drugs to treat alopecia and exhibits significant potential in clinical applications. This work is financially supported by the Guangdong Basic and Applied Basic Research Foundation (2019B1515120043 and 2022A1515012154) and the Key Fields of Biomedicine and Health Foundation of Colleges and Universities in Guangdong Province (2022ZDZX2017).