Background. Dexamethasone is sometimes used as a coanalgesic because of its anti-inflammatory properties. Objective . To evaluate opioid use, postoperative pain intensity, and side effects after a single dose of dexamethasone in patients undergoing arthroscopic knee surgery. Methods . In this randomized controlled study patients were randomized to receive either 10 mg of intravenous dexamethasone (DM group) or 0.9% normal saline (NS group) during the intraoperative period. Primary outcomes were pain intensity and total morphine and codeine use after surgery. Results . Seventy-eight patients were included in the study. The DM group showed statistically significant higher pain intensity at the fourth postoperative hour (DM: 3.96/10, standard deviation [SD] 0.54; NS: 2.46/10, SD 0.45;<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"><mml:mi>p</mml:mi><mml:mo>=</mml:mo><mml:mn fontstyle="italic">0.036</mml:mn></mml:math>). No statistically significant difference in total opioid use (morphine plus codeine) was identified with 15.9 (SD 1.97) codeine tablets used in DM group and 20 (SD 2.14) in NS group (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M2"><mml:mi>p</mml:mi><mml:mo>=</mml:mo><mml:mn fontstyle="italic">0.25</mml:mn></mml:math>). Discussion . Pain intensity tended to decrease in both groups suggesting morphine as the main source of analgesia. Conclusions . Intravenous dexamethasone during the intraoperative period has no clinical impact on postoperative pain intensity during the first 48 h after arthroscopic knee surgery. This trial is registered with R000020892 .