This work was fulfilled to assess the effect of supplementation diets with Basil oil in buffalo calves on growth performance criteria, rumen fermentation properties and certain biochemical indices. A total number of 18 buffalo calves of (4-6) months age and 141.29 kg average body weight were classified randomly into three equal groups (6 animals each): Animals of T1 (control) were fed on basal diet and those of T2 and T3 (treated) were fed as T1 plus 2 and 4 ml basil oil (BO) per head daily, respectively. This experiment was expanded for fifteen weeks. Blood plasma and rumen liquor Samples were obtained from all experimental animals in all groups at the finishing of study for detecting certain blood biochemical parameters and rumen fermentations properties. Results showed that the groups supplemented by basil oil (T2 and T3) recorded significant improvement (P≤0.05) in DM intake, digestibility, growth performance and best feed conversion ratio compared with control group (T1). Also, treated groups (T2 and T3) recorded non observable (P≥0.05) effects in TVFA's, total protozoa count (TPC) and ammonia concentration compared with control group. Blood plasma analysis in supplemented groups (T2 and T3) showed significant improvement (P≤0.05) in protein profile (total protein and albumin), non-significant decrease in urea, creatinine, triglycerides, liver function enzymes levels in comparing with control group. The results collected from this study proposed that buffalo calves fed diets supplemented with basil oil as an essential oil, showed greater total weight gains, daily weight gains, and feed conversion rates with better rumen fermentation parameters.