Dietary inclusion of alternative feedstuffs (AF) could impact animal performance, ruminal ecosystem, and/or blood parameters. The objective of the current trial was to evaluate the effects of dietary inclusion of mixed AF on hematological and biochemical parameters of growing lambs. Male Awassi lambs (n = 27, average BW = 20.0 ± 0.5 kg and average age of 90 days) were randomly assigned to one of three dietary groups (9 lambs/group). Diets were formulated to contain (on DM basis) 0 (CTL; conventional diet without AF), 25% (25AF), or 50% (50AF) of mixed AF (dry bread, carob pods, olive cake, and sesame meal). Blood samples were collected from each lamb before morning feeding at the beginning (7 days after the start), middle (day 35), and end (68 day) of the study. Hematological parameters were not affected (P ≥ 0.11) by treatment diets. Except for urea N and cortisol, dietary treatments had no significant (P ≥ 0.07) effects on serum levels of all of the measured metabolites and enzymes. Lambs fed the 50AF diet had the lowest blood level of urea N and cortisol. The current study demonstrates that dietary inclusion of AF up to 50% did not negatively impact lambs’ health assessed with changes in hematological and biochemical parameters.