This study assessed the impact of the dietary inclusion of l-ascorbic acid and organic zinc (Availa-Zn) on heat-stressed Japanese quails. Growth performance, antioxidant status, immune status, heat shock protein 70 (HSP70), and some blood biochemical parameters were assessed. One-day-old, unsexed Japanese quail chicks (n = 240) were randomly allocated into 4 dietary treatments (6 replicates per treatment; 10 birds per replicate). Birds were fed a basal corn-soybean meal diet (control treatment) with different supplemental levels of l-ascorbic acid and/or Availa-Zn (200 mg l-ascorbic acid/kg diet, 62 mg Availa-Zn/kg diet, and 200 mg l-ascorbic acid + 62 mg Availa-Zn/kg diet) from July to August 2020 for 35 days. The average minimum and maximum ambient temperatures varied from 85.4 to 98.8 °F, and the relative humidity was between 69 and 74%. Supplemented l-ascorbic acid and Availa-Zn, either as separate supplements or as combined supplements, increased bird growth performance, blood hemoglobin, thyroid hormones, total protein, globulin, total antioxidant capacity, HSP70, catalase, superoxide dismutase enzyme activity, and immunoglobulin A and G (P < 0.05), while heterophil/lymphocytes decreased (P < 0.01) during the entire rearing period (1–35 days). Most of the assessed parameters showed stronger responses when l-ascorbic acid and Availa-Zn were added together, which may suggest a synergistic effect. In conclusion, the com- bined supplementation of l-ascorbic acid and Availa-Zn at 200 and 62 mg/kg, respectively, could be considered an efficient dietary supplement to enhance Japanese quail growth performance, antioxidant capacity, immune status, and general health under heat stress conditions.