BackgroundThis study aims to provide a comprehensive understanding of maternal risk factors, infant risk factors and maternal infant feeding practices among refugees and migrants along the Thailand-Myanmar border.MethodsThis study employed a mixed-methods approach with two components: (1) cross-sectional survey (n = 390) and (2) focus group discussions (n = 63). Participants were chosen from one of three clinics providing antenatal and delivery services for Karen and Burman refugees and migrants along the border. Participants were pregnant women and mother-infant dyads.ResultsRefugee and migrant mothers demonstrated high rates of suboptimal breastfeeding and low rates of minimum dietary diversity and acceptable diet. Multivariable regression models showed infant stunting (AOR: 2.08, 95% CI: 1.12, 3.84, p = 0.020) and underweight (AOR: 2.26, 95% CI: 1.17, 4.36, p = 0.015) to have increased odds among migrants, while each 5 cm increase in maternal height had decreased odds of stunting (AOR: 0.50, 95% CI: 0.38, 0.66, p < 0.001) and underweight (AOR: 0.64, 95% CI: 0.48, 0.85, p = 0.002). In addition, small-for-gestational-age adjusted for length of gestation, infant age and gender increased odds of infant’s stunting (AOR: 3.42, 95% CI: 1.88, 6.22, p < 0.001) and underweight (AOR: 4.44, 95% CI: 2.36, 8.34, p < 0.001). Using the Integrated Behavioural Model, focus group discussions explained the cross-sectional findings in characterising attitudes, perceived norms, and personal agency as they relate to maternal nutrition, infant malnutrition, and infant feeding practices.ConclusionsInadequate infant feeding practices are widespread in refugee and migrant communities along the Thailand-Myanmar border. Risk factors particular to maternal nutrition and infant birth should be considered for future programming to reduce the burden of chronic malnutrition in infants.