The aim of this study was to investigate associations of birth weight with sociodemographic variables, domestic violence, ways of coping, social support, and general mental health of Iranian mothers. Six hundred mothers aged 15 to 29 years participated between June 2009 and November 2010. t-Test, analysis of variance, Spearman’s correlation, and multiple regression were used. The results showed that there was no significant association between birth weight and general mental health of the mothers. Prenatal care visits, the mothers’ history of having children with low birth weight (LBW), and weight gain during pregnancy were significantly associated with birth weight. The women who reported physical abuse during pregnancy had infants with lower birth weight. Satisfaction with social support and use of positive reappraisal were significantly associated with higher birth weight. In conclusion, a high quality of prenatal care and screening of pregnant women are recommended. Social environments good enough during pregnancy have protective effects against LBW.