This study examined the effects of self-differentiation and psychological discomfort on antenatal attachment of pregnant couples in their third trimester of pregnancy. The subjects were 182 couples in J province who had participated in the first wave of the Korea Attachment Longitudinal Study (KALS). Data were analyzed by means of frequency, percentages, Pearson's correlations, and stepwise multiple regression models using SPSS 20.0. The findings were as follows. First, the independent t-test showed that the mean scores of pregnant women’s self-differentiation were lower than their spouses in all subscales except emotional cutoff, and higher than in all psychological discomfort subscales. There was no significant difference in antenatal attachment quality between women and men, but the pregnant women significantly spent more time thinking about the fetus than their spouses. Second, the stepwise multiple regression models revealed that pregnant women’s emotional cutoff in self-differentiation influenced the most on both quality and quantity of antenatal attachment. Among subscales of their spouses’ self-differentiation, only emotional reactivity had an impact on quality of antenatal attachment, and fusion with others had the most impact on quantity of antenatal attachment. Among the pregnant women’s and their spouses’ psychological discomfort subscales, only depression influenced each quality and quantity of antenatal attachment. This is the very first and only study in which the impact of the pregnant couples’ self-differentiation on antenatal attachment has been examined.