This study aimed to comparing the effect of peritonsillar infiltration of tramadol and dexmedetomidine in relieving post-tonsillectomy pain. In this randomized double blinded clinical trial study, 90 children 5-12years old undergoing tonsillectomy, involved. Induction of anesthesia was done by fentanyl 1µg/kg, sodium thiopental 5mg/kg and atracurium 0.5mg/kg and intubation was done after 3min. Anesthesia maintained by nitrous oxide 60% and oxygen 40% with isoflurane (1.2%). Tramadol 2mg/kg in group A, dexmedetomidine 1µg/kg in group B, and normal saline in group c were injected into the bed and anterior tonsillar pillar and surgery has begun after 3min of injection. Time of surgery, all hemodynamic variables, pain intensity and degree of sedation were recorded and evaluated. The results showed that duration of the surgery (p value = 0.28) and duration of anesthesia (p value = 0.43) were not significantly different between the groups but pain score was significantly lower in dexmedetomidine group in comparison to tramadol and placebo group (p value = 0.001). The first time for analgesic request was longer in dexmedetomidine group (p value = 0.001) and Hemodynamic parameters were significantly lower in tramadol and dexmedetomidine group (p value = 0.001). Sedation level was not significantly different between tramadol and dexmedetomidine group (p value = 0.001). According to the results peritonsillar infiltration of dexmedetomidine is effective and safe in relieving post-tonsillectomy pain.