Background: Arterio-venous fistulas (AVFs) are the vascular access of choice for hemodialysis (HD) with a lower incidence of complications and longer survival than prosthetic grafts or central venous catheters. Objective: To evaluate the role of color Doppler ultrasound (CDUS) in the detection and characterization of complications of arterio-venous fistula (AVF) dialysis access. Patients and methods: The study was carried out at the Department of Radiology, El-Zaitoun Specialized Hospital, Cairo. The study was carried out during the period between August 2020 till April 2021. A total of 50 patients were selected from those referred from the nephrology dialysis center. All patients were subjected to assessment of AVF complications by CDUS. Results: Out of 50 patients with complicated AVF of them, 22 patients (44%) were males, and 28 patients (56%) were females. The total complications frequencies were 65. Of them venous thrombosis was found in 24 patients (37%), stenosis in 17 patients (26%), aneurysm in 13 patients (20%), pseudoaneurysm in 5 patients (8%), hematoma in 3 patients (5%), clinical suspicion of infection in 2 patients (3%), and steal phenomenon/syndrome in 1 patient (1%). Conclusion: The CDUS was a non-invasive diagnostic tool for early detection of complications of AVF that allowed monitoring of the AVF blood flow, and detection of possible causes of vascular access malfunction. Owing to its low cost and availability, it was used as the first-line imaging modality for non-functional AVF.