A cross-section study was undertaken to determine the prevalence of ptosis (congenital and acquired) and its risk factors in Iranian children. The target population was children aged seven years in urban areas of Iran. Seventy schools of eight cities were included leading to participation of 4106 children; 41.8% were male. Fifty-eight cases of ptosis were found – 20 unilateral. Prevalence of ptosis was reported as 1.41%: 0.49% unilateral and 0.93% bilateral. Prevalence of ptosis with amblyopia was 42.75% and prevalence of strabismus was higher in subjects with bilateral ptosis. Severe astigmatism was significantly more prevalent with ptosis, especially with-the-rule type.