This study aims to improve the functional properties of robusta coffee by adding crude gambir extract. A completely randomized non-factorial design with 5 treatments is used and each treatment was repeated three times. The treatments consist of: robusta coffee powder (%): crude gambir extract (%) F1 = 100:0, F2 = 95:5, F3 = 90:10, F4 = 85:15, and F5 = 80:20. The results showed that the addition of crude gambir extract has a significant effect on increasing the total phenol value from 10.65 to 101.20 mg/mL GAE and the antioxidant activity with an IC50 value of 583.06 to 40.10 µg/mL, acidity level (5.43-5.51), and the solubility percentage of 27.55-31.15%. Furthermore, the addition of crude gambir extract have no significant effect on the taste, color, and aroma of the functional coffee produced.