Background: Diastolic function has been reported to be impaired in many patients with coronary slow flow phenomenon (CSFP). CSFP has broad spectrum of clinical presentations, including non- ST elevation myocardial infarction (NSTEMI). We sought to study the short-term evolution of diastolic function in CSFP patients presenting with NSTEMI. Methods: This study included 92 patients with CSFP and acute NSTEMI. Conventional echocardiography Doppler imaging (CDI) and tissue Doppler echocardiography imaging (TDI) were used to evaluate diastolic function during index NSTEMI and after 3 months. Results: Mean age of study patients was 45.7 ± 6.8 years. The prevalence of diastolic dysfunction at baseline was 69 patients (75%) and 28 patients (30.4%) at 3 months, p< 0.001. Various diastolic function indices showed significant improvement from baseline to three months follow up. E/Em was 17.32 ± 3.41 at baseline compared to12.41 ± 5.58 at 3 months, p=0.039. Septal e’ velocity was 5.67±4.56 cm/s at baseline compared to 7.78±3.22 cm/s at 3 months, p= 0.023. Medications used were not significantly different between those with improved versus unimproved diastolic dysfunction (DD). Conclusion: Diastolic function seems to improve over short term follow up in patients with CSFP presenting with NSTEMI. This could reflect a transient worsening during acute NSTEMI.