This study was conducted to evaluate the effect of cold water during summer season of Upper Egypt in different times on growth performance, carcass traits and economical efficiency of New Zealand white rabbits. The experimental rabbits were reared in batteries and equally distributed into four groups (8 rabbits/each) in open housing system. The rabbits of first group (C) were full-fed ad libitum with tap water. In the other treated three groups, the birds of second, third and fourth groups (T1, T2 and T3) were supplied with cold water at different times: 1000-1300h, 1300-1600h and 1000-1600h, respectively. The results indicated that time of cold water in open housing system did significantly affect live body weight, body weight gain, feed intake, feed conversion and water consumption. Also, the group which received cool water at 1000-1600h showed the best records for decreased levels of rectal temperature and respiratory rate. However, no significant differences were existed in blood protein, lipids, globulin, cholesterol and carcass traits percentages. It could be concluded that most of growth performance and physiological parameters of examined rabbits were significantly decreased by heat stress under Egyptian summer conditions. Applying drinking cold water during the period from 1000 to1600h resulted to improve growth performance and economical efficiency.