Taiwan has over the past three decades been experiencing demographic changes that may pose important concerns for children's quality of life. This study examines the relationships and potential pathways between family structure transitions and early childhood development. Our analysis is based on 19,499 children from the 2005 birth cohort who completed three follow-up surveys (at 6, 18, and 36 months of age). Using multiple regressions, we found that children who consistently lived with single parents or who experienced their parents' divorce/separation did poorer in both cognitive and socioemotional development than those in stable married families. Significance testing for mediation by bootstrapping revealed that the disparities could be explained by the family's exposure to income poverty, psychosocial functioning and/or parenting quality. It is important to look more deeply into sociocultural factors in future investigations.