Gac fruit (Momordica cochinchinensisSpreng) is mostly found in southeast Asian countries. Previous studies have demonstrated that gac fruit is a major source of β-carotene, lycopene, and α-tocopherol. This study aimed to develop the extraction of Thai gac fruit as a potential active ingredient for antioxidant, melanogenesis, and collagen stimulating activities. In the present study, different parts of ripe Thai gac fruit, the peel, pulp, and seed membrane, were extracted using the accelerated solvent extraction (ASE) technique, an innovative plant extraction method. DPPH radical-scavenging activity, ABTS radical scavenging activity, and ferric reducing/antioxidant power (FRAP) assay were performed to compare the antioxidant activity derived from each part of the fruit. The effect of Thai gac fruit on melanogenesis and collagen stimulating activities was investigated using B16F1 and human fibroblast cell lines, respectively. The results demonstrate that the pulp (EC50value of 7.42 ± 0.81 mg/mL) and the seed membrane (EC50value of 76.43 ± 2.66 μg/mL) showed the strongest antioxidant activities in DPPH and ABTS assay, respectively. The peel clearly displayed the strongest antioxidant activity and significantly increased the FRAP value (247.67 ± 19.73 μM/mg). Furthermore, the peel showed the lowest melanin content (76.56 ± 7.13 % of control) in the B16F1 cell line, and clearly increased the most amount of collagen (21.87 ± 3.12%) in the human fibroblast cell line in comparison to the other fractions. Therefore, Thai gac fruit peel revealed the biological effects, including antioxidant, melanogenesis, and collagen stimulating activities. In conclusion, Thai gac fruit extracted using the ASE technique exhibited several effects that could be used as a potential active ingredient for cosmeceutical products, due to its antioxidant, melanogenesis, and collagen stimulating activities. Our findings provide potential uses of Thai gac fruit as a multifunctional cosmeceutical ingredient to be further explored in future studies.