Aim: Inflammatory bowel disease (IBD): [Crohn’s disease (CD) or ulcerative colitis (UC)] is characterised by chronic inflammation with multisystemic effects. Myocardial dysfunction may occur during active disease due to increased inflammation. The aim of our study is to evaluate the effect of disease activity index at diagnosis on myocardial functions in children with IBD in remission. Materials and Methods: The study consisted of 34 IBD patients and 21 healty children. Patients were divided into two groups according to disease activity at the diagnosis as mild and severe disease activity. Conventional echocardiography and strain echocardiography was performed for all study patients. Results: In IBD patients with severe disease activity at diagnosis, global longitudinal strain of left ventricle (GLLV), longitudinal strain (AP3) and (AP4) were lower than patients with mild disease activity at the diagnosis (p=0.043, p=0.032, p=0.028, respectively). Disease activity at the diagnosis was inversely correlated to ejection fraction (%), strain values of GLLV, left ventricle apical chamber (LVAP) 3, LVAP2 in UC patients. (p=0.047, p=0.016, p=0.029, p=0.011, respectively). Mitral E, DT was lower in IBD patients than control patients (p=0.05, p=0.04). Strain value of LVAP4 was lower in CD patients, than UC patients (p=0.046). Strain values of GLLV, LVAP3, LVAP4 was decreased in CD patients than control patients (p=0.046, p=0.046, p=0.048). Mitral E and desceleration time were found to be decreased in IBD patients than control patients (p=0.05, p=0.04 respectively). Conclusion: Our study revealed that the severity of disease activity at diagnosis has long-term effects on myocardial functions.