Sheep as an experimental animal has been used in many veterinary researches. The developmental study of the ovine cervicothoracic ganglion in the fetal stages will reveal the anatomy of the sympathetic nervous system in the adult sheep and morphological and morphometrical relation between this ganglion and surrounding structures. The aim of this research was to follow morphological and morphometrical development of cervicothoracic ganglion in sheep during fetal stages and its relation to the body sides and sex. This study was performed on 18 ovine fetuses. The approximate age of fetnses were 11 to 16 weeks and were divided in 3 groups. Coalescence of the caudal cervical ganglion and few primary ganglia of the thoracic part of sympathetic trunk were morphologically studied. In Morphometrical studies, the length and width of the ganglia were measured. The results were statistically analyzed using 1-way ANOVA. The caudal cervical and first thoracic ganglia were the most frequent cervicothoracic ganglion. Variations in the length and width of ganglia between 11 to 16 weeks were not significant (p> 0.05), but with increasing of age interval become significant (p<0.05). There were not any correlation between length of ganglia and side of body and sex (p> 0.05). The results of this study can be useful for evaluation of developmental and cell changes in neuropeptides of the sympathetic ganglia especially cervicothoracic ganglion.