According to some studies, the number of addicted females in reproductive ages has been increased. The present study was designed to investigate the effect of oral morphine consumption on the development of CNS and body growth in rats. For this purpose, female Sprauge-Dawley rats were divided into control and experimental groups (20 animals in each group). Maintenance dose of morphine (0/4 mg/ml) was administrated as the final dose and continued to the end of lactation period. After delivery, pups were investigated for mortality and their sex, congenital malformation, skull dimensions, and wet weight of the brain and volume of the brain. The duration of hair growth and eye opening was also considered. The results indicated that sex ratio (male/female) was 1.40 and 1.54 in experimental and control groups respectively. No congenital malformation was also observed. Meanwhile, weight in experimental group gradually significantly decreased to the end of lactation period. Duration of hair growing and eye opening of experimental group also showed a 1-day delay as compared to control group. At postnatal day 14, skull height in male significantly decreased, while skull width significantly increased in female. Wet weight of the brain significantly increased in both male and female rats. Volume of the brain also significantly decreased in male and female rats. At postnatal day 21, skull length in female significantly decreased. Volume of the brain also significantly decreased in male and female rats. It is concluded that the maximal effect of oral morphine administration on the developmental of the brain may appear at postnatal day 14 in rats.