This study aimed to investigate the impact of adding Zahdi date juice on the physicochemical characteristics and microbiological analysis of bio-yogurt with a probiotic starter (St. thermophilus, Lb. acidophilus, and B. longum) and haematological parameters in mice. The bio-yogurt was prepared by adding a 5% probiotic starter supplemented with date juice at 2, 5, and 10% (v/v). Hematological parameters: Mice (n = 30) were divided into five groups (Tc, T1, T2, T3, and T4) and treated with either a standard diet or a standard diet enriched with 3 ml/day of bio-yogurt containing 0, 2, 5, and 10% date juice for 30 days. The results showed that the addition of date juice increased the acidification rate, decreased pH values, and improved the syneresis of bio-yogurt. During the 21-day period, the viability of probiotic bacteria decreased, but a bio-yogurt sample containing 10% date juice had a higher number of probiotic bacteria than the other samples. The diet and body weight of the mice were affected by the daily administration of bio-yogurt or bio-yogurt with date juice. In addition, the groups treated with bio-yogurt, including date juice, typically had superior haematological parameters and better immunity levels than other groups (P ≤ 0.05). Compared with the control group, mice administered bio-yogurt containing date juice showed reduced total cholesterol and triglyceride levels. In conclusion, the addition of date juice to the bio-yogurt improved the physicochemical properties and increased the viability of probiotic bacteria as well as improving the blood parameters of experimental animals.