Cannulation of the arteriovenous fistula is a critical step in haemodialysis but it is also associated with several potential complications. This chapter addresses the most common cannulation-related issues, including haematomas, difficult cannulation, bleeding, and infection. Haematomas may compromise the fistula function and limit cannulation sites, while repeated failed attempts increase the risk of vessel damage. Bleeding can result from improper technique or fistula dysfunction, and infections may lead to local or systemic complications. Strategies for prevention, early recognition, and management are discussed, emphasizing the importance of proper technique, staff training, and standardized protocols to ensure patient safety and preserve the vascular access.