Abstract Cascara contains antioxidants and polyphenols that can be used as additives in probiotic drinks, such as soy milk yogurt. The purpose of this study was to determine the physicochemical, microbiological, and sensory characteristics of soy milk yogurt with the addition of cascara extract. The experimental design used RAL (Completely Randomized Design) factorially with different lengths of fermentation for 8 hours, 12 hours, 24 hours, and variations in the addition of cascara extract concentrations of 0.5%, 1%, and 1.5% (b/v). This research method was carried out by making soybean juice, making cascara extract, and continuing to make soy milk yogurt with the addition of cascara extract. The results showed that yogurt had a pH value in the range of 3.24-3.63, color L in the range of 64.32-62.06, color a* in the range of -1.7 to -0.35, color b* in the range of 7.55-8.79, viscosity in the range of 475.33-771.67, protein content in the range of 2.86%-4, 92%, antioxidant activity range 7.69%-51.47%, total titratable acid range 0.88%-1.30%, total lactic acid bacteria (LAB) range 7.11 log CFU/ml to 8.38 log CFU/ml. The result showed that the best treatment was the 24-hour fermentation treatment with the addition of 1% and 1,5% cascara extract. Abstrak Cascara memiliki kandungan antioksidan dan polifenol yang dapat digunakan sebagai bahan tambahan pada minuman probiotik contohnya yoghurt susu kedelai. Tujuan dari penelitian ini yakni untuk mengetahui karakteristik fisikokimia, mikrobiologis, dan sensori yogurt susu kedelai dengan penambahan ekstrak cascara. Rancangan percobaan menggunakan RAL (Rancangan Acak Lengkap) secara faktorial dengan perbedaan lama fermentasi selama 8 jam, 12 jam, 24 jam dan variasi penambahan konsentrasi ekstrak cascara yaitu 0,5%, 1%, 1,5% (v/v). Metode penelitian ini dilakukan dengan pembuatan sari kedelai, pembuatan ekstrak cascara, dan dilanjutkan pembuatan yoghurt susu kedelai dengan penambahan ekstrak cascara. Hasil penelitian menunjukkan bahwa yoghurt memiliki nilai pH kisaran 3,24-3,63, warna L kisaran 64,32-62,06, warna a* kisaran -1,7 hingga -0,35, warna b* kisaran 7,55-8,79, viskositas kisaran 475,33-771,67, kadar protein kisaran 2,86%-4,92%, aktivitas antioksidan kisaran 7,69%-51,47%, total asam tertitrasi kisaran 0,88%-1,30%, total Bakteri Asam Laktat (BAL) kisaran 7,11 log CFU/ml hingga 8,38 log CFU/ml. Hasil penelitian menunjukkan perlakuan terbaik yaitu pada perlakuan fermentasi 24 jam dengan penambahan ekstrak cascara 1% dan 1,5%.