OBJECTIVE To determine the frequency of amblyopia and its associations among children with congenital ptosis. METHODS A retrospective chart review of 92 active patients with congenital ptosis in the practices of 2 of the authors. The main outcome measures were relative eyelid ptosis severity, presence and type of strabismus, refractive error, and amblyopia. RESULTS Amblyopia was identified in 22 of 92 patients (23.9%), in almost every case occurring in the context of coexisting anisometropia or strabismus and affecting the eye with the more severe ptosis (P = 0.0001). Amblyopia was more likely to occur in cases with greater relative eyelid asymmetry and did not develop in children with symmetric ptosis. In several cases, anisometropia and amblyopia were not initially apparent but progressively developed during follow-up. CONCLUSIONS Children with congenital ptosis are at risk of anisometropic and strabismic amblyopia, which may progress during early development. Patients should be examined at regular intervals to evaluate and treat these potential complications.