This experiment was aimed to study the effect of nutmeg leaf tannin addition on in vitro nutrient digestibility. Treatments in this experiment consisted of: P0 (control without tannin), P1 (feed + 2% tannin) and P2 (feed + 4% tannin). Feed for fermentation substrate consisted of Pennisetum purpureum and soybean meal with ratio 60:40. Fermentation was carried out using Tilley and Terry two stages in vitro technique for 48 hours. Variables measured were the digestibility of dry matter, organic matter, and crude protein in the rumen as well as the total digestive tract digestibility based on in vitro technique. The data obtained were analyzed by One Way ANOVA, and followed by the Duncan Multiple Range Test (DMRT). The results showed that rumen dry matter digestibility was lower (P0.05) in the total dry matter digestibility of P0, P1, and P2 (74.88±5.28, 67.70±3.21, and 64.83±4.96). Organic matter digestibility in the rumen was also lower (P0.05) in total organic matter digestibility from P0, P1, and P2 (64.69±6.44, 64.33±6.34, and 61.20±5.11). The digestibility of crude protein in the rumen at P1 and P2 (45.48±5.12 and 38.47±3.44) was also significantly lower (P0.05). Addition of tannin leaf nutmeg 2% optimally reduced rumen dry matter and crude protein digestibility without causing excessive negative impact on results of in vitro digestibility, so it can be used as a protective agent protein feed.