Diastolic function usually declines before systolic function, and this precedes clinical signs in patients with acute coronary syndrome. Therefore, diagnosis of diastolic dysfunction is very important for early diagnosis, follow-up, treatment, and prognostic evaluation in heart failure with preserved ejection fraction (HFpEF) patients. The main objective of the study was to find out association between prolonged QTc dispersion and left ventricular diastolic dysfunction in Non ST Segment Elevation Myocardial Infarction (NSTEMI) patients in HFpEF. This cross sectional analytical study was conducted in the Department of Cardiology and 60 patients were included as study population from August 2015 to July 2016. Then the study population was divided into two groups, each group consisted of 30 patients. NSTEMI patients with prolonged QTc dispersion treated as Group I and NSTEMI patients with normal QTc dispersion treated as Group II. The study shows 20.0% vs. 26.6% patients had detected as Grade I in Group I and Group II respectively with statistically insignificant association (p=0.16). On the contrary, 30.0% vs. 13.4% patients had detected as Grade II in Group I and Group II respectively with statistically significant association (p=0.001). Again, 40.0% vs. 10.0% patients had detected as Grade III in Group I and Group II respectively with statistically significant association (p=0.001). QTc dispersion was found sequentially significant increased (p=0.007) among 3 grades of LVDD (63.6±4.9 vs. 79.4±8.6 vs. 98.2±28.8). QTc dispersion in surface ECG which is a cheap, non-invasive, easily available tool can help us predicting left ventricular diastolic dysfunction in patients with NSTEMI.