Background Women's participation in decision-making in the household is an indicator of women's empowerment. Few studies have compared domestic decision-making power and its effect on postpartum health between immigrant and native-born women. This study aimed to examine the effect of domestic decision-making power and social support during pregnancy on predicting postpartum depressive and physical symptoms among immigrant and nativeborn mothers in Taiwan. Methods and findings This prospective study recruited 177 marriage-based immigrant mothers and 230 nativeborn women who were at least twelve weeks pregnant from hospitals, clinics and health centers. Data were collected in the 2nd or 3rd trimester of pregnancy and at 3 months postpartum from March 2013 to March 2015. Postpartum depression and the severity of postpartum physical symptoms were measured using the Edinburgh Postnatal Depression Scale, and a 17-item, 4-point Likert scale, respectively. Linear regression was used to examine the relationship between "domestic decision-making power and social support during pregnancy" and "depressive and physical symptoms at 3 months postpartum." Women who had lower domestic decision-making power and social support during pregnancy had higher postpartum depressive and physical symptoms. Those women with full-time employment and insufficient family income had higher postpartum depressive symptoms. Though immigrant women scored lower in domestic decision-making power and social support than native-born women, they had lower mean scores in postpartum depressive and physical symptoms. After accounting for the abovementioned factors, immigrant women remained at lower risk for postpartum depressive and physical symptoms than native-born women. There was significant interaction between domestic decision-making power and immigrant status, suggesting that the association between domestic decision-making and postpartum depressive and physical symptoms was smaller for immigrants than for native women. Conclusions Domestic decision-making power and social support during pregnancy are protective predictors of postpartum depressive and physical symptoms. However, the effect of domestic decision-making power appeared to be less salient for immigrants, probably due to the "healthy immigrant effect" and/or lower expectations toward domestic decision-making power among immigrants. The finding that immigrant women demonstrated a lower level of domestic decision-making power suggests that empowerment issues need to be addressed among immigrants.