Introduction: Considering the spread of Covid-19, it is important to know its complications. In the present study, we examined the frequency of patients with myocarditis and Kawasaki disease and related demographic and laboratory findings in children before and during covid-19. Materials and methods: The present study was carried out in a descriptive-analytical manner on patients with myocarditis or Kawasaki disease during the years 2016 to 2016. During this study, demographic information, laboratory variables of the child were collected from the patients' files and statistically analyzed using SPSS version 24 software. Findings: In this study, 65 patients (31 girls and 34 boys) with an average age of 41.28 ± 3.9 months were examined. Of these, 46 people (69.7%) had Kawasaki disease and 19 (28.8%) had myocarditis. The condition of being infected with Covid-19 was also observed in 22 of the patients (33.3%). The rate of hospitalization with the diagnosis of Kawasaki disease after Covid-19 was significantly higher than before [27 cases (58.7%) against 19 cases ( 41.3%)], while the hospitalization rate with the diagnosis of myocarditis decreased significantly after the onset of corona [1 case (5.3%) vs. 1 case (5.3%), (P<0.001)]. Conclusion: According to the results, the hospitalization rate with the diagnosis of Kawasaki disease after the occurrence of covid-19 was significantly higher than before, and the frequency of patients with Kawasaki disease with and without covid-19 was not significantly different.