Coparenting has been defined as the mutual support and coordination between the parents relative to the education and the caretaking of their child(ren). Studies have shown that parental personality factors are predictive of the aptitude to collaborate in the coparental interaction. Parental self-esteem is one of the variables that influence parenting and coparenting. Coparenting may in turn influence parental self-esteem. This longitudinal study aimed at exploring the interplay between coparenting and self-esteem during the first two years of the child’s life. Maternal and paternal self-esteem have been taken into account as both parents contribute to the coparental dynamics. In total, 68 two-parent families were received in our laboratory at three time points (3, 9 and 18 months postpartum). The procedure included self-reported measures of parental self-esteem – along two dimensions: satisfaction and sense of efficacy in the parental role – as well as direct observation of coparenting behaviors in the PicNic game situation. Results showed that parental self-esteem and the quality of coparenting behaviors are stable from 3 to 18 months, except for paternal sense of efficacy, which increases over time. Moreover, positive increases in paternal sense of efficacy were linked with a higher coparenting at baseline, and with a decrease in coparenting from 3 to 18 months. Clinical implications of these results are discussed.