Objectives: This study aims to evaluate left ventricular (LV) function using global longitudinal strain (GLS) in patients with coronary slow flow (CSF) and to compare myocardial deformation between treated and untreated groups. Patients and methods: Between October 2022 and October 2024, a total of 52 patients (25 males, 27 females; mean age: 55.8+/-1.1 years, range, 44 to 67 years) diagnosed with CSF were included. Thirty-two patients received pharmacological treatment, while 20 were untreated. Transthoracic echocardiography including two-dimensional (2D) speckle-tracking was performed to assess LV GLS. Clinical data and comorbidities were recorded. Results: The mean age of the untreated group was higher than the treated group (59.5+/-1.1 vs. 52.8+/-6.4 years, p=0.001). Global longitudinal strain was significantly reduced in untreated patients (-17.26+/-0.56) compared to treated patients (-22.28+/-1.17) (p=0.001). Conventional LV ejection fraction was normal and similar in both groups. Conclusion: Strain echocardiography is a sensitive tool for detecting subclinical LV dysfunction in CSF. Pharmacological treatment correlates with improved myocardial strain, indicating potential myocardial protection. Early diagnosis and treatment may improve cardiac outcomes in CSF patients.