Background: Intraarticular bupivacaine produces sufficient analgesia after arthroscopic knee surgery, but its analgesic duration is short. There is a need to search for an adjuvant with a longer duration of analgesia. Objectives: This study aimed to compare the duration of analgesia, total rescue analgesic consumptions, pain intensity, adverse effects, and patient satisfaction of dexmedetomidine and fentanyl as adjuvants to intraarticular bupivacaine for analgesia after knee arthroscopy. Study Design: A prospective double-blind randomized controlled study. Setting: Zagazig University Hospitals. Methods: After ending arthroscopy and 15 minutes before deflation of the tourniquet, 45 patients were randomly allocated into 3 equal groups: Group B (n = 15) received an intraarticular injection of 50 mg (20 mL) bupivacaine 0.25% plus 1 mL saline; group BD (n = 15): received an intraarticular injection of 20 mL bupivacaine 0.25% plus 100 µg (1 mL) dexmedetomidine; and group BF (n = 15) received an intraarticular injection of 20 mL bupivacaine 0.25% plus 50 µg (1 mL) fentanyl. Results: The BF group had a statistically significant longest duration of analgesia (693.3 ± 22.6 minutes) compared to group the BD (505.8 ± 23.5 minutes) and group B (244.1 ± 17.5 minutes) (P < 0.0001). The total meperidine consumption was statistically significantly decreased in group BF (35 ± 12.6 mg) compared to the BD and B groups (60 ± 12.6 mg and 83.3 ± 15.4 mg respectively) (P < 0.0001). Groups BF and BD showed a highly statistically significant lower postoperative static and dynamic pain scores at 30 minutes, 1, 2, 4, and 6 hours compared to group B. However, group BF was comparable to group BD at the same time intervals. Postoperative static and dynamic pain scores showed a highly statistically significant higher values at 4 hours in group B, 8 hours in group BD, and 12 hours in group BF (P < 0.0001). No significant side effects were observed in the groups. The duration of analgesia was the most important parameter that determined patient satisfaction. Limitations: Small sample size and lack of studies that compare both adjuvants. Conclusions: Fifty µg of fentanyl as an adjuvant to intraarticular bupivacaine produces effective and safe analgesia after knee arthroscopy as 100 µg of dexmedetomidine and has a longer analgesia duration in the first postoperative 24 hours.