OBJECTIVE To evaluate the association between craniofacial phenotype and hearing loss in children with craniofacial microsomia. DESIGN Retrospective cohort study. SETTING Tertiary care children's hospital. PATIENTS Individuals with craniofacial microsomia. MAIN OUTCOME MEASURES Ear-specific audiograms and standardized phenotypic classification of facial characteristics. RESULTS A total of 79 participants were included in the study. The mean age was 9 years (range, 1 to 23 years) and approximately 60% were boys. Facial anomalies were bilateral in 39 participants and unilateral in 40 participants (24 right, 16 left). Microtia (hypoplasia of the ear) was the most common feature (94%), followed by mandibular hypoplasia (76%), soft tissue deficiency (60%), orbital hypoplasia or displacement (53%), and facial nerve palsy (32%). Sixty-five individuals had hearing loss (12 bilateral and 53 unilateral). Hearing loss was conductive in 73% of affected ears, mixed in 10%, sensorineural in 1%, and indeterminate in 16%. Hypoplasia of the ear or mandible was frequently associated with ipsilateral hearing loss, although contralateral hearing loss occurred in 8% of hemifaces. CONCLUSIONS Hearing loss is strongly associated with malformations of the ipsilateral ear in craniofacial microsomia and is most commonly conductive. Hearing loss can occur contralaterally to the side with malformations in children with apparent hemifacial involvement. Children with craniofacial microsomia should receive early diagnostic hearing assessments.