This study aimed to investigate the biological activities of Tectona grandis L. f. related to hair loss treatment, including steroid 5α-reductase (S5AR) inhibition, effect on Human Follicle Dermal Papilla Cells (HFDPCs), anti-testosterone activity, cytotoxicity on macrophage cells and interleukin 1 beta (IL-1β) secretion inhibition. Among the crude extracts, T. grandis leafhexane and ethyl acetate (EtOAc) extracts possessed potent S5AR inhibitions, with IC50 values of 31.39±3.38 µg/mL and 20.92±2.59 µg/mL, respectively. T. grandis leaf-hexane extract showed lower cytotoxicity on HFDPCs than EtOAc extract. Hexane extract at 25 µg/mL had similar anti-testosterone activity with a positive control, finasteride, and exhibited 70% inhibition of IL-1β secretion in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. Meanwhile, EtOAc extract had lower anti-testosterone activity at 6.25 µg/mL and exhibited 52% IL-1β secretion inhibition at 1.5 µg/mL. This discovery suggests T. grandis leaf extracts as a new source of active ingredients for the development of hair care products.