In order to study the effects of thyme and garlic powder on ingestion and in vivo digestibility of nutrients in guinea pigs, a study was carried out at the Teaching and Research Farm (TRF) of the University of Dschang. The trial was done according to a factorial design (ration and sex) in four batches of 5 males and 5 females each. Thus, 40 guinea pigs weighing 450 ± 50 g, and four rations (T0, T1, T2 and T3) were used. The control ration allocated to the animals in batch 0 contained no additive. The animals of batches 1, 2 and 3 respectively received 1% thyme powder; 1% garlic powder and 0.5% thyme + 0.5% garlic powder in their rations. Forage, Trypsacumlaxum was given ad libitum as basal feed. From this study it was recorded that regardless of sex and for any sex combined, feed intake of dry matter, organic matter, crude protein and crude fiber remained comparable. Likewise, the ingestion of composed feed was comparable between females receiving T0 (21.93 g DM / d / animal), T1 (23.20 g DM / d / animal) and T2 (23, 46 g DM / d / animal), but significantly higher than that of females subjected to the T3 ration (12.20 g DM / d / animal). In addition, females receiving T3 ration significantly ingested dry matter and organic matter better than the males. Regarding a DC, those of crude fiber were on one hand comparable in males subjected to T0 (90.92%) and T1 (89.83%) rations, but significantly better than those of males subjected to T2 (86.28%) and T3 (86.18%) rations in which these a DC were also comparable. According to the results obtained, the ingestion and in vivo digestibility of nutrients in guinea pigs can be improved by using thyme powder at the level of 1% in the ration.