<p>The present study aimed to evaluate the effect of dietary inclusion of mealworms (<i>Tenebrio molitor</i>) in the form of larvae and whole insects on growth performance, rumen fermentation parameters, selected health indicators, and economic efficiency in growing Ossimi lambs. Eighteen Ossimi lambs, aged 4 to 5 months with an initial weight of 23.7 ± 2&#xa0;kg, were arbitrarily allocated into three identical groups. The control group was fed a basal ration consisting of a concentrate feed combination at 2% according to body weight and fed wheat straw freely, without any additives; the larvae mealworm (LMM) group was provided with a basal diet supplemented with (1g/kg) of LMM powder; and the insect mealworm (IMM) group was administered a basal diet enhanced with (1g/kg) of IMM powder. At the beginning of the trial, animals were weighed in the morning before feeding and every two weeks during the experimental period (120 days). The findings indicated that the LMM and IMM groups exhibited increased final BW, total gain, and daily gain increase relative to the control group, but the differences were not significant. The feed efficiency based on dry matter (DM) and total digestible nutrients was comparable across the three groups. However, digestible crude protein was considerably elevated (<i>P</i> = 0.024) in group IMM relative to the control and other groups. The LMM and IMM groups had considerably greater amounts of DM, organic matter, and carbohydrates than the control group. In the control group, blood albumin and glucose levels were higher, whereas blood globulin levels were lower compared to the LMM and IMM groups (<i>P</i> &lt; 0.05). The economic return and return on investment were numerically higher in the LMM and IMM groups in comparison with the control group. In conclusion, the inclusion of mealworms (either larvae or complete insects) in ruminant diets may improve animal production and profitability without negatively impacting animal health.</p>