Two experiments were carried out to evaluate the effects of supplementing different levels of nano emulsified essential oils blend (NEOB) (oregano, garlic, and clove oil)  on in-vitro rumen gas production, rumen fermentation and lactating goats performance. The first experiment designed to study the effect on in-vitro gas production and rumen fermentation parameters, while, the second experiment to study the effect on lactating goat's performance trail. Fifteen Shami lactating goats, were divided into three similar groups (5 animals each). The experimental groups were (T1) the control group, were fed on (50% concentrate feed mixture :50 % roughage). While the second group (T2) and third group (T3) were fed on the control ration supplemented with 5 ml NEOB /head/day or 7.5 ml NEOB /head/day respectively. The results showed that, experimental animals which fed on NEOB groups showed reduction of in vitro Gas production GP (ml/200mg DM), GPSF (ml/g DM), GPSNF (ml/g DM) and SCFA (mml/ml gas) (p < 0.05) when compared with the control group.  Animals of (T3) group showed significantly (P<0.05) the highest values of milk yield, milk protein content, fat, TS, Ash, lactose, actual daily and fat-corrected (4% fat) daily milk yield, followed by group (T2). However, the control group (T1) recorded the lowest milk yield among all groups. Results of feed conversion ratio (FCR) in the terms of DM kg / kg 4% fat corrected milk (FCM), showed that the group supplemented with 7.5 ml NEOB/animal/day gave significantly (P<0.05) better values than the control group. Milk yield from animals of Group T1 recoded significantly (P<0.05) higher total saturated fatty acids content (SFAs), while, those of T2 and T3 recorded higher significant (P<0.05) values of total poly-unsaturated fatty acids ((C22:6), (C18:3), (C20:2), (C20:3), (C20:4), (C20:5), (C22:5), (C18:2)). The animals of T3 recorded (P<0.05) the highest albumin and globulin, immunity values in term of (IgG and IgM) and GPx (U/mg protein) antioxidant followed in a decreasing an order by T2 and T1, respectively.