The purpose of this study was to identify the factor structure of the Neonatal Eating Assessment Tool–Breastfeeding (NeoEAT–Breastfeeding) and to assess its psychometric properties, including internal consistency reliability, test–retest reliability, and construct validity as measured by concurrent and known-groups validity. Exploratory factor analysis conducted on responses from 402 parents of breastfeeding infants younger than 7 months old showed a 62-item measure with seven subscales and acceptable internal consistency reliability (Cronbach's α = .92). Test–retest reliability was also acceptable (r = .91). The NeoEAT–Breastfeeding has evidence of concurrent validity with the Infant Gastroesophageal Reflux Questionnaire (r = .69) and Infant Gastrointestinal Symptoms Questionnaire (r = .62). The NeoEAT–Breastfeeding total score and all subscale scores were higher in infants with feeding problems than in typically feeding infants (p < .001, known-groups validity). The NeoEAT–Breastfeeding is a parent-report assessment of breastfeeding in infants from birth to 7 months old with good initial evidence of reliability and validity.