The aim of the study was to compare the effects of peritonsillar infiltration of tramadol before and after the surgery on post-tonsillectomy pain. In this double-blinded clinical trial study, 80 children aged 5-12 years old with ASA (American Society of Anesthesiologists) class I or II undergoing tonsillectomy involved. In group A (n = 40), after anesthesia induction and before starting the surgery, tramadol 2 mg/kg diluted in normal saline up to 2 cc total volume was injected into the tensile bed by the anesthesiologist using a 25 gauge needle. Surgery began 3 min later and the tonsils were removed using the sharp dissection method. In children of group B (n = 40), anesthesia induction was performed. When surgery was completed, tramadol 2 mg/kg diluted in normal saline up to 2 cc total volume was injected at the site of removing each tonsil using a 25 gauge needle by the anesthesiologist. Using the CHEOPS (Children's Hospital of Eastern Ontario Pain Scale) Scale, pain recorded at different times. Patient sedation was recorded using the RAMSAY Sedation Scale. All the data were analyzed using SPSS 17 statistical software. Two groups significantly felt different pain intensities at different times following the surgery. At the three times, the mean sedation score in the group receiving tramadol infiltration before surgery was a little higher compared to the other group, but this difference was not significant (p > 0.05). As for the relative frequency of nausea and vomiting, the difference was not significant (p = 0.793). Request for analgesics between the groups was not significant (p = 0.556). The mean time of the first feeding after the surgery was not significant between the groups (p = 0.062). Surgical duration was almost the same for both groups (p > 0.05). Systolic blood pressures (before surgery, before extubation, and after extubation) were statistically the same in both groups (p < 0.05). Furthermore, systolic blood pressures 10, 15, and 30 min after entry into the recovery room were the same in both groups. We concluded that peritonsillar infiltration of tramadol before surgery controlled postoperative pain better from 8 h after the surgery to hospital discharge (late effect), but that local infiltration of tramadol after surgery controlled postoperative pain better up to 2 h after the operation (early effect).