The purpose of this study is to determine the effects of exercise on serum thyroxine level and the number of cerebral cells of congenital hypothyroid rat. This research is experimental, pretest- posttest control group and posttest control group design. Twelve Sprague Dawley rats, aged 4-5 months, healthy and ready to mate were divided into 6 groups that is (1) Normal, (2) Normal exercise, (3) Hypothyroidism, (4) hypothyroidism thyroxine, (5) Hypothyroidism exercise, and (6) hypothyroidism thyroxine exercise . Hypotiroid rat were induced 0.025% prophilthiourasil (PTU) in drinking water is starting on the pregnant day-5 to Lactation day-15. The pups began adapted to exercise in the wheel since the age of 17 days and increased exercise duration up to 30 minutes per day at the age of 30 to 60 days. FT4 levels were measured in pregnant mother, children aged 3 weeks and the end of the treatment that is at the age of 2 months, and taken blood and brain. The number of pyramid and neuroglia cells count of brain histological preparations with HE staining. Statistical analysis using one way ANOVA test and the Kruskal Wallis, and poshoc. Mean FT4 levels (ng / dL) to normal rat, normal exercise, hypothyroidism, hypothyroid exercise, hypothyroidism thyroxine, and hypothyroidism thyroxine exercise respectively 1.32 ± 0.20, 1.77 ± 0.11, 0.50 ± 0.09, 1.46 ± 0.37, 1.50 ± 0.2 and 1.20 ± 0.33 (p <0.05). The highest number of pyramid cells found in hypothyroid thyroxine exercise rats group, followed by normal exercise rat s group, and the lowest was found in hypothyroid group (p <0.05). There were no significant differences in the number of neuroglia cells (p,> 0.05). Exercises improve serum thyroxine level and increasing the number of pyramid cells significantly