Separation anxiety is a common reaction when preschool children start school, but in some children it persists and hinders adjustment. This narrative review synthesizes research on the manifestations of, factors associated with, and support strategies for separation anxiety in preschool children at school entry. The literature was searched in Scopus (06 October 2026) and supplemented with PubMed and the reference lists of key articles. Separation anxiety declines over time in most children, but a small group shows persistently high anxiety that warrants early identification. Associated factors include child temperament, family context, mother–child attachment, and parental anxiety. The strongest evidence concerns interventions involving parents, whereas evidence for universal school-based strategies remains limited. Implications for practice and directions for future research in Vietnam are discussed.