<p>Climate change-induced heatwaves have increased the prevalence of heat stress (HS) in livestock, negatively impacting their physiology and productivity. Moringa leaves offer a feasible strategy through their acknowledged antioxidant, antimicrobial, and anti-inflammatory benefits. Consequently, this study aimed to investigate the dietary effects of dried Moringa oleifera leaves (MOL) on the growth performance, hematological indices, thyroid function, blood biochemistry, immunity, and economic revenue of growing crossbred calves (Holstein Friesian × Baladi) under heat stress (HS) conditions. A total of 30 growing calves were randomly allocated into three equal groups (<i>n</i> = 10). Experimental treatments consisted of a control basal diet (MOL0) and two levels of dried <i>Moringa oleifera</i> leaf (MOL) supplementation (0.3% (MOL0.3) and 3% (MOL3) of the diet) for 60 days during HS condition. The values of THI were 88.4, indicating severe HS during experimental conditions. The results demonstrate that final body weight (FBW), total weight gain, and average daily gain (ADG) were significantly enhanced in both MOL-supplemented groups compared to the control group (<i>p</i> &lt; 0.01). Specifically, the MOL3 group exhibited the most substantial improvements across all growth metrics. Dietary inclusion of 0.3% or 3% MOL significantly increased serum concentrations of thyroid hormones (T₃ and T₄) and immunoglobulins (IgM and IgG) compared to the control group (<i>p</i> &lt; 0.01). All MOL-treated groups exhibited significantly higher antioxidant enzyme activities (TAC, GPx, CAT, and SOD) and lower MDA levels than the stressed control (<i>p</i> &lt; 0.01). Dietary inclusion of MOL significantly modulated hematological parameters and increased total protein concentrations compared to the control group (<i>p</i> &lt; 0.01). Dietary MOL effectively mitigated the physiological imbalance caused by HS, as evidenced by a significant decrease in liver enzymes (AST, ALT, and ALP) and lower concentrations of urea and creatinine (<i>p</i> &lt; 0.001). Notably, serum α-amylase and glucose levels were significantly elevated in the treatment groups (<i>p</i> &lt; 0.001). Dietary fortification with MOL significantly reduced blood lipid accumulation in growing calves, as evidenced by significantly lower levels of total cholesterol, LDL, VLDL, and TG compared to the control group (<i>p</i> &lt; 0.001). Economically, the 3% MOL supplementation strategy resulted in the highest net income, with 0.3% MOL yielding the second highest. These findings demonstrate that dietary inclusion of MOL in growing calves exposed to HS effectively enhances thermal resilience and improves growth indices through the regulation of immune responses, augmentation of antioxidant capacity, and modulation of blood biochemical profiles. Consequently, MOL supplementation represents a feasible nutritional strategy to combat the deleterious impacts of heatwaves in the context of climate change, thereby promoting a more sustainable cattle production system.</p>