BACKGROUND: Brachiocephalic arteriovenous fistula (AVF) i s t he p referred v ascular a ccess f or c hronic k idney d isease (CKD) patients undergoing hemodialysis due to its lower complication rate and superior patency compared to other access types. One potential predictor of cannulation success is vessel wall thickness assessed through intima-media thickness (IMT). However, the association between IMT and cannulation success remains inconclusive. This study aimed to evaluate the relationship between IMT and cannulation success in brachiocephalic AVF. METHODS: This observational analytic study with a cross-sectional design included 60 CKD patients with mature brachiocephalic AVFs undergoing their first cannulation at Cipto Mangunkusumo Hospital and Hermina Depok Hospital (April-September 2025). IMT was measured using ultrasonography, and cannulation success was defined as the absence of complications (hematoma/thrombosis). Statistical analysis was performed using independent T-Test, Mann-Whitney, and χ2/Fisher Exact tests, with P<0.001 considered significant. RESULTS: Of 60 patients, 42 (70%) had successful cannulation, while 18 (30%) experienced complications. The mean IMT was significantly higher in the successful group compared to the unsuccessful group (0.117 vs. 0.082 mm; P<0.001). ROC analysis yielded an AUC of 0.972 (95% CI: 0.925-1.000; P<0.001), with an optimal cut-off value of 0.1 mm providing 100% sensitivity and 88.9% specificity. No significant differences in IMT were observed based on diabetes mellitus or hypertension status. CONCLUSIONS: IMT is significantly associated with cannulation success in brachiocephalic AVFs and can serve as a reliable predictor, with a cut-off value of 0.1 mm. © 2025 EDIzIONI MINERVA MEDICA.