Evaluate impact of the marjoram and parsley by-products on rumen fermentation characteristics (in vitro) and the productive performance of early lactating buffaloes (in vivo) are the main objectives of this study. Two in vitro experiments were conducted to evaluate the effect of partial and full substitution of control ration's rice straw by marjoram and parsley by-products on rumen fermentation characteristics. In the in vivo study; fifteen lactating buffaloes after 2 weeks of calving were randomly assigned into three groups using complete random design. Buffaloes were fed dry matter according to 3% of their body weight for 60 days. The first animal's group was fed on the control ration (60% CFM and 40% rice straw). The second group was fed 60% CFM and 40% parsley by-products (CP100), while the third group was fed 60% CFM and 40% marjoram by-products (CM100). The results indicated that full replacement of rice straw by marjoram (CM100) and parsley (CP100) by-products led to 1) significant (P < 0.05) increased in vitro degradability of ration's DM, OM, NDF and ADF with improving all ruminal basic parameters (pH, NH3-N, TVFA, s, SCFA and total gas production. 2) significant (P<0.05) increased in ability of the lactating buffaloes for more digestion of diet's DM, OM, CP and NFE. The buffaloes fed (CP100) ration had higher (P<0.05) blood plasma protein, albumin and globulin with higher (P<0.05) milk, 4% fat corrected milk (FCM) and all milk component yields. It could be concluded that; parsley by-products significantly enhance buffalo's milk production with no harmful effects on their health and we recommend them as roughage sources, especially in the summer.