Previous studies have reported the harmful effects of exposure to phthalic acid (PA) on heart. No studies have reported the effects of prenatal PA exposure on the structure or function of heart. The current study aimed to investigate the effects of prenatal PA exposure on the markers of oxidative stress and cardiac structure in rats' offspring. Twenty-four pregnant rats were randomly categorized into three groups of control, exposed to 2.5 and 5 % PA. The morphometric properties of coronary arteries, markers of oxidative stress, and NOS activity were measured in offspring rats. By a dose-dependent manner, the body weight (BW), heart weight (HW), and HW/BW of the intervention groups were reduced and their heart rate and blood pressure were conversely increased compared to the control group. Also, the wall thickness, cross-sectional area of the aorta and septal branch of the descending left coronary artery were significantly increased in the intervention group. In addition, PA significantly increased the level of malondialdehyde and decreased the level of superoxide dismutase and glutathione peroxidase, compared to the control group. This study revealed that prenatal exposure of rats to PA causes vascular dysfunction, increasing oxidative stress, and reduction in cardiac nitric oxide synthetase activity among offspring rats.