Emerging evidence suggests that maternal and child dietary diversity are associated. Data on mother-child (6 to 24 months) dyads in Bangladesh, Viet Nam, and Ethiopia were used to examine agreement and association between maternal and child dietary diversity and identify determinants of maternal and child dietary diversity. There was mother/child agreement for staple foods across the three countries but disagreement for flesh foods, dairy, fruits, and vegetables. The odds of achieving minimum dietary diversity (≥ four groups) were higher among children whose mother consumed four groups compared with ≤ three food groups. Maternal education was associated with both maternal and child dietary diversity; food security and socioeconomic status were associated only with maternal dietary diversity. Because maternal dietary diversity is strongly associated with child dietary diversity, diverse diets should be promoted for both mother and child during the entire span of the first 1000 days.