Teo tuber starch (Tacca leontopetaloides (L.) Kuntze) has potential as a substitute for sago flour in the production of bagea cookies. This study aimed to analyze the proximate composition and evaluate the organoleptic acceptance of bagea cookies substituted with teo tuber starch. The study used an experimental method with a quantitative descriptive approach involving five treatments of teo tuber starch substitution in the production of bagea cookies. The observed parameters included proximate analysis (carbohydrates, protein, fat, crude fiber, moisture, and ash contents) and organoleptic evaluation (color, taste, aroma, and texture) using 35 panelists. Proximate data were analyzed descriptively, while organoleptic data were analyzed using the Kruskal-Wallis test. The best treatment was determined using the De Garmo effectiveness index. The results showed carbohydrate content ranging from 76.83–82.53%, protein content from 1.98–3.32%, fat content from 4.78–8.92%, crude fiber content from 2.24–4.06%, moisture content from 4.41–7.62%, and ash content from 0.95–3.99%. The De Garmo effectiveness index values for the proximate analysis of F1–F5 were 0.4066, 0.8677, 0.5710, 0.2824, and 0.5739, respectively, with F2 identified as the best treatment. The organoleptic test showed that substitution did not result in significant differences (p>0.05) in color, taste, aroma, or texture. Bagea cookies substituted with teo tuber starch were accepted by the panelists at a moderately preferred level. Based on these results, the De Garmo effectiveness index values for the organoleptic evaluation of F1–F5 were 1.000, 0.552, 0.320, 0.280, and 0.040, respectively, with F1 identified as the best treatment.