The Bayley's Scales of Infant and Toddler Development-Third Edition (Bayley-III) were used to measure the development of 24-month-old children (N = 1,452) in the Interactions of Malnutrition and Enteric Infections: Consequences for Child Health and Development (MAL-ED) study (an international, multisite study on many aspects of child development). This study examined the factor structure and measurement equivalence/invariance of Bayley-III scores across 7 international research sites located in Bangladesh, Brazil, India, Nepal, Pakistan, Peru, and South Africa. Exploratory and confirmatory factor analyses were used to identify the factor structure of Bayley-III scores. Subsequently, reliability analyses and item response theory analyses were applied, and invariance was examined using multiple-indicator, multiple-cause modeling. The findings supported the validity, but not invariance, of Bayley-III language scores at all seven sites and of the cognitive and motor scores at six sites. These findings provide support for the use of scores for research purposes, but mean comparison between sites is not recommended.