Objectives: This study aimed to assess the prevalence and impact of magnesium depletion on ischemic cardiomyopathy with non-sustained ventricular tachycardia (NSVT) patients. Methods: 35 consecutive ischemic cardiomyopathy patients with (NSVT) were grouped according to presence or absence of magnesium depletion to (G1 and G2). Holter ECG was done on admission then repeated at the 4th day thereafter. Rhythm abnormalities as well as QT variability index (QTVI) were assessed, magnesium depletion was assessed by urinary magnesium measurement, magnesium loading test (MLT), and fractional magnesium excretion. Magnesium infusion then given to magnesium-depleted patients for 3 days. Results: 71.4% of our study population had magnesium depletion, of those; 48% had normal serum magnesium level. Patients with magnesium depletion had higher frequency of baseline episodes of NSVT (p = 0.001), the frequencies of PVCs/hour, couplets, ventricular tachycardia runs and NSVT episodes were significantly decreased after the magnesium infusion within the same group (G1) and relative to the other group (G2) (p = 0.04, 0.043, 0.02 and 0.001 respectively), patients of G1 had significantly higher baseline QTVI than those of group 2 (p < 0.03), baseline QTVI was decreased after IV magnesium replacement in G1 (p<0.001). Conclusion and recommendation: The prevalence of magnesium depletion in ischemic cardiomyopathy with NSVT at our study was 71.4%. Serum magnesium level could be normal despite magnesium depletion. Patients with magnesium depletion on top of ischemic cardiomyopathy are at an increased risk of both NSVT and increased QTVI. We recommend to improve clinician awareness about magnesium depletion detection by fractional magnesium excretion and MLT instead of relying on serum magnesium level, magnesium supplementation in patient with NSVT on top of ischemic cardiomyopathy reduces the frequency of ventricular arrhythmia and probably may decrease the risk of SCD.