Objective: The purpose was to determine the risk of sensorineural hearing loss (SNHL) in young infants with abnormal head sizes in a developing country. Materials and Methods: A matched case-control study of two (hospital-based and community-based) cohorts of term infants who failed a two-stage hearing screening test with transient-evoked otoacoustic emissions and automated auditory brainstem response in Lagos, Nigeria. Abnormal head size (microcephaly or macrocephaly) was determined with World Health Organisation's growth standards for head circumference. The adjusted odds ratios for the risk of SNHL in microcephalic and macrocephalic infants were established through unconditional and conditional logistic regression analyses. Results: Some 194 cases and 970 matched controls drawn from 8,872 term singletons 3 months or younger were studied. The median age of enrolment was 1 day in the hospital-based cohort and 17 days in the community-based cohort. Microcephalic infants in both cohorts were significantly at risk of SNHL while no significant risk was found among macrocephalic infants regardless of birth setting. Conclusions: Microcephalic infants should be routinely screened for potential hearing loss particularly where universal newborn hearing screening is not immediately practicable. Etiological investigation of abnormal head size in this and similar population is warranted. Routine screening and maternal immunization for congenital infections should also be considered.