Chronic renal failure patients undergoing hemodialysis complain of moderate pain from repeated punctures of the arteriovenous fistula. This study examined the optimal application time of thermotherapy for reducing pain, anxiety, and side effects during arteriovenous fistula puncture. This study was conducted as a single-blinded randomized controlled trial. The participants were arteriovenous fistula puncture patients with chronic renal failure who were divided into two thermotherapy groups and one control group. This study was approved by the institutional review board and registered with the Clinical Research Information Service (KCT0003768). Differences between groups regarding pain, anxiety, and side effects were analyzed using one-way ANOVA, the χ2 test, and the Scheffé test. A significant difference was observed between the 10-min and 20-min thermotherapy groups and the control group in terms of the pain they experienced. Additionally, more side effects were encountered in the 20-min thermotherapy group than in the 10-min group. The 10-min application of thermotherapy for an arteriovenous fistula puncture showed the same pain-reducing effect as the conventional 20-min application. The study confirmed a 10-min application of thermotherapy to be an effective nursing intervention for pain relief without side effects.