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