Background: Knee arthroscopy is usually associated with a variable degree of pain ranging from moderate-to-severe pain in about 70% of patients. Objective: This trial was designed to assess the efficacy of intra-articular administration of dexamethasone versus fentanyl as adjuncts to bupivacaine in patients undergoing arthroscopic knee surgery. Patients and methods: Eighty-nine patients of either sex were enrolled in this study. The patients were randomly divided into three equal groups. Group F that received intra-articular (IA) injection of 1 μg/kg fentanyl (In 2 ml saline) added to 18 ml of 0.25% bupivacaine, group D, which received IA injection of 8 mg (2 ml) dexamethasone added to 18 mL of 0.25% bupivacaine and group S that received IA injection of 2 ml normal saline added to 18 mL of 0.25% bupivacaine. Results: The time required for the first request of analgesia in group F, group D, and group S was 5.7 ± 0.7 vs 4.5 ± 0.5 vs 3.3 ± 0.5 hours respectively. There were significant differences between both treatment groups and the control group (p < 0.001) and in between both treatment groups (p < 0.001) in favor of group F. There was a significantly lower median visual analogue score in group F when compared to group D and S at 6 hours (p = 0.006 & 0.01, respectively), 12 hours (p < 0.001 & < 0.001, respectively), and 18 hours (p = 0.003 & 0.007, respectively) postoperatively. Conclusion: The addition of fentanyl or dexamethasone to IA bupivacaine in knee arthroscopic surgery provided a better quality of analgesia with less consumption of systemic analgesics without significant adverse effects.