The purpose of this study was to investigate the stability and reciprocal effects of maternal parenting stress and perceived social support in early childhood. Specifically, we compared these relations for working and nonworking mothers. The second through fourth wave data of the Panel Study of Korean Children (PSKC) were used in this study. Data were analyzed using t-tests, correlations, and autoregressive cross-lagged modeling analyses. First, parenting stress of non-working mothers was higher than that of working mothers and working mothers perceived higher levels of social support compared to nonworking mothers. Second, both maternal parenting stress and social support were stable over time. Third, there were significant reciprocal effects between maternal parenting stress and perceived social support. Differences between working and non-working mothers were found in the paths from parenting stress to social support. The implications of the stability and reciprocal effects of parenting stress and perceived social support and the difference between working and non-working mothers in the relationship of the two constructs have been discussed.