The primary purpose of this study is to examine transactional relationships among children's negative emotionality, mothers' depression, and parenting behavior using the autoregressive cross-lagged model. Methods: Data were drawn from the 2nd (T1) through 4th (T3) wave (2009-2011) of the Panel Study on Korean Children (PSKC). A total of 1,535 mothers of 1-to 3-year-old children participated in this study. Results: First, mothers' parenting behavior at T1 and T2 had significant effects on children's negative emotionality at T2 and T3, respectively, whereas children's negative emotionality did not predict the mothers' parenting behavior. Second, transactional relationships were confirmed between mothers' depression and parenting behavior from T1 to T3. Third, transactional relationships were found between children's negative emotionality and mothers' depression from T1 to T3. Lastly, children's negative emotionality at T1 and parenting behavior at T3 were mediated by mothers' depression at T2. Conclusion: The present study found that the parent effects in the relationship between children's negative emotionality and mothers' parenting behaviors, and identified the transactional relationships between children's negative emotionality and maternal depression, as well as between maternal depression and parenting behavior in early years of life.