Family income strongly influences child development. However, the impact of variation in family income over time on developmental outcomes is unclear. Using nationally representative data of children in poor and moderate income families and three relevant theoretical frameworks, the purpose of the present study was to (a) empirically classify family income trajectories using income-to-needs ratios during early childhood, (b) examine demographic characteristics of children and families in each respective class, and (c) evaluate associations between derived income trajectories and kindergarten outcomes. Results identified four distinct family income trajectory profiles, including stable adequate, low to adequate, stable low, and adequate to low. The majority of children in the present study were classified in the stable low trajectory (67%) and most of these children (55%) fluctuated above and below 100% of federal poverty guidelines at various times throughout early childhood. Multiple regression results suggested children in the stable low trajectory demonstrated poorer kindergarten outcomes than children in more advantaged trajectories. Furthermore, children who experience economic disadvantage early with later income growth display poorer reading outcomes than children who were economically advantaged initially and experience later income decline. Multinomial logistic regression findings posit birth, child, and family characteristics such as maternal depression, maternal work status, and household composition differentiate income trajectory class membership. Findings are discussed in the context of current dialogue about the nature of family poverty over time, and the inadequacies of social policy responses that attend to family needs at one-point-in time without consideration of trajectories and the consequences of cyclical poverty on early childhood academic and social and emotional development.