Seven jersey calves, one week old, were assigned to two treatment groups. A control group (3 animals) with no L-ascorbic acid supplementation and a supplemented group (4 animals) receiving 2gm/head daily of L-ascorbic acid for 3wk period. Treatments were switched in a crossover design for another 3wk period. At the end of each period animals were exposed to direct sunlight for 2 h. respiration rate (Rr) and rectal temperature (Rt) were recorded. Heat tolerance was calculated using Road's coefficient and some blood constituents were measured, before and after exposure to sunlight. Direct sunlight exposure increased Rr (P<.001), Rt (P<.001) and serum glucose in control (P<.01) and treated animals (P<.07) and increased total bilirubin (P<.03), in only, and GOT and GPT and decreased PVC% in both groups. However, L-ascorbic acid supplemented-animals had lower Rr (P.001), Rt and serum glucose. Cholesterol, total bilirubin (P<.01), GOT (P<.01) and albumin (P<.05) concentrations. PVC% and heat tolerance were higher in supplemented than in control when the animals were exposed to direct sunlight. Dietary  ascorbic acid may improve heat tolerance and blood profile of suckling jersey calves exposed to direct sunlight.