Introduction: Oral hygiene in children and parental awareness have an important role in prevention of infective endocarditis. The aim of this study was to determine oral and dental health in children with congenital heart disease in comparison with a control group and its relation with knowledge, attitude and performance of parents.Materials and Methods: In this cross-sectional descriptive-analytical study carried out in 2012, 60 children, aged 3‒12 years, with congenital heart disease, referring to a private pediatric cardiology clinic and 60 healthy children, selected randomly, were evaluated. Then DMFT/dmft, plaque index and gingival index were recorded and a questionnaire was completed by parents for evaluating their knowledge, attitude and performance. Data were analyzed with SPSS 16 by descriptive statistics, 2-sample t-test, and chi-squared and regression tests (a=0.05).Results: The means of DMFT/dmft, PI and GI in children with CHD were significantly higher compared to healthy children (p value = 0.001). Parents’ knowledge and attitude had no significant relationship with children’s mean PI, GI and DMFT/dmft (p value > 0.05); however, parents’ performance and mean DMFT/dmft were significantly related (p value = 0.01), with no significant relationship with PI and GI (p value > 0.05). There were no significant differences in knowledge and performance between the two groups (p value > 0.05); however, parents’ attitudes in the patient group were significantly more positive that the healthy group (p value = 0.004).Conclusion: Children with CHD had lower oral health than healthy children. Parental knowledge and performance about heart disease and the importance of oral health was low. However, the attitude of parents of children with CHD was more positive than other group, indicating the role of education in improving attitude.