Purpose: This study was conducted to determine the impacts of maternal depression on the temperament, health problems, and development of 4-month-old infants. Methods: For this longitudinal comparative study, data collected at one month postpartum and at the 4th month of follow-up were evaluated from sixty five pairs. The Edinburgh Postnatal Depression Scale (EPDS) was used to assess the symptoms of depression. Results: Eighteen point 5 percent and15.4% of mothers were diagnosed with postpartum depression at one month post-partum and at the 4th month of follow-up, respectively. The temperament of the infants between the two groups was not different. However, the infants of the depressed mothers had more health problems after 4 months. Depressed mothers had a lower score for the acceptance of Home Observation for Measurement of the Environment (HOME), and the development score of their infants was lower than that of the non-depressed mothers. Conclusion: Maternal depression affects the health and development of infants. Women should be screened for potential risk factors and for symptoms of depression during postpartum periods so that appropriate interventions including emotional support can be initiated in a timely manner.