Objectives: There are a number of potential advantages to performing hysteroscopy in an outpatient setting. However, the ideal approach, using local uterine anesthesia or rectal non-steroidal anti-inflammatory drugs, has not been determined. Our objective was to compare the efficacy of intrauterine lidocaine instillation with rectal diclofenac for pain relief during diagnostic hysteroscopy. Methods: We conducted a double-blind randomized controlled trial on 70 nulliparous women with primary infertility undergoing diagnostic hysteroscopy. Subjects were assigned into one of two groups to receive either 100mg of rectal diclofenac or 5mL of 2% intrauterine lidocaine. The intensity of pain was measured by a numeric rating scale 0–10. Pain scoring was performed during insertion of the hysteroscope, during visualization of the intrauterine cavity, and during extrusion of the hysteroscope. Results: There were no statistically significant differences between the groups with regard to the mean pain score during intrauterine visualization (p=0.500). The mean pain score was significantly lower during insertion and extrusion of the hysteroscope in the diclofenac group (p=0.001 and p=0.030, respectively). Nine patients in the lidocaine group and five patients in diclofenac group needed supplementary intravenous propofol injection for sedation (p=0.060). Conclusions: Rectal diclofenac appears to be more effective than intrauterine lidocaine in reducing pain during insertion and extrusion of hysteroscope, but there are no significant statistical and clinical differences between the two methods with regard to the mean pain score during intrauterine inspection.