Cardiac dysfunction due to cardiotoxicity from anthracycline chemotherapy is a leading cause of morbidity and mortality in survivors of childhood cancer. The intraventricular pressure gradient (IVPG) of the left ventricle (LV) is the suction force of blood from the left atrium to the LV apex during early diastole and is a sensitive indicator of diastolic function. We assessed IVPG as a new indicator of the cardiac dysfunction in survivors of childhood cancer after anthracycline therapy. We performed a prospective echocardiographic study on 40 survivors of childhood cancer aged 6–26 years who received anthracycline therapy (group A) and 53 similar-age normal controls (group N). The subjects were divided into the younger groups, N1 and A1 (age < 16 years); older groups, N2 and A2 (age ≥ 16 years). IVPG was calculated using color M-mode Doppler imaging of the mitral inflow using Euler’s equation. Total IVPG was divided into the basal and mid-to-apical IVPG to demonstrate more clearly the mechanisms of the LV diastolic suction force. The total anthracycline dose was 16.2–600.0 mg/m² (median 143.5 mg/m²). Total IVPG significantly decreased in group A2 compared with that in group N2 (0.39 ± 0.07 vs. 0.29 ± 0.11 mmHg/cm; p = 0.010). The mid-to-apical IVPG significantly decreased in groups A1 and A2 compared with that in groups N1 and N2, respectively (N1 vs. A1: 0.20 ± 0.05 vs. 0.16 ± 0.05 mmHg/cm, p = 0.036; N2 vs. A2: 0.21 ± 0.06 vs. 0.14 ± 0.06 mmHg/cm, p = 0.001). Basal IVPG, E wave, and E/e′ were not significantly different between patients and normal controls. The total and mid-to-apical IVPG, especially mid-to-apical IVPG, could be sensitive new indicators in survivors of childhood cancer after anthracycline therapy.