The sociopolitical context of Norway includes low poverty rates and universal access to subsidized and regulated Early Childhood Education and Care (ECEC). In this context, the association between family income dynamics and changes in early child behavior problems was investigated, as well as whether high-quality ECEC buffers children from the effects of income dynamics. In a population-based sample (N = 75,296), within-family changes in income-to-needs predicted changes in externalizing and internalizing problems (from ages 18 to 36 months), particularly for lower income children. For internalizing problems, ECEC buffered the effect of income-to-needs changes. These findings lend further support to the potential benefits of ECEC for children from lower income families.