The purpose of this study was to evaluate the effect of dietary betaine supplementation on growth characteristics and some blood constituents of Ossimi rams. A total of 18 Ossimi rams were randomly divided into three equal groups, considering their body weight. Animals of the first group (Co) served as control, while animals of the second (BET1) and third (BET2) groups offered 2 and 4 g of betaine/head/day, respectively. At the last day of the experiment, blood samples were taken to estimate some blood metabolites. Three digestibility experiments were carried out to determine nutrients digestibility and nutritive values of the rations. Body weight was recorded while average daily gain, feed conversion and feed economic efficiency were calculated. The results show that betaine supplementation to rams either with 2 or 4 g/head/day increased (P≤0.05) plasma total protein, plasma globulin, plasma glucose and triiodothyronine hormone (T3), while it significantly (P≤0.05) decreased A/G ratio and plasma total cholesterol. Concentrations of plasma albumin and plasma urea N did not differ significantly due to betaine supplementation. Digestibility coefficients of DM, OM, CP, EE and CF were significantly (P≤0.05) increased for BET2 group than for BET1 and Co groups. However, NFE digestibility was not influenced by betaine. The TDN value was increased (P≤0.05) for BET2 diet compared with other treated diets. While, the nutritive values as DCP did not significantly differ among treatments. Animals in BET1 and BET2 consumed more (P≤0.05) metabolizable energy (ME, Mcal/kg) compared with the control group. Live body weight did not differ (P>0.05) among groups while average daily gain and total weight gain were improved (P≤0.05) in treated groups. Feeding Ossimi rams on BET1 increased significantly (P≤0.05) daily dry mater intake (DMI), and total digestible nutrient intake (TDNI) when compared with BET2 and Co groups, while treated groups consumed (P≤0.05) metabolizable energy (ME) more than the control group. Daily digestible crude protein intake (DCPI) did not significantly differ among treatments. In conclusion, dietary betaine supplementation to Ossimi rams could modify some metabolic processes, and enhance feed consumption and energy mobilization which could be reflected on improving the productive performance.