The aim of this prospective single-blinded and controlled study is to evaluate the efficacy of levobupivacaine infiltration on post-tonsillectomy pain relief in adults. The study was conducted with 40 adult patients who underwent tonsillectomy. These patients were randomized in either study group (SG) who received levobupivacaine infiltration to peritonsillary fossae prior to surgery or control group (CG) with no medication. After surgery, all the patients were queried for pain scores by visual analog scale. In addition, the volume of intraoperative bleeding, the duration of operation, the severity of postoperative complications, and the amount of analgesic requirement were the other outcome measures of this study. There were significant differences between groups regarding pain scores for the first 24 h in favor of SG. The analgesic requirement was also significantly lower in SG (p = 0.009). Although there was a sustained decrement at pain score during first 24 h for SG, however, the change from baseline score (immediate score) for each time interval revealed no significance compared to CG. In addition, the duration of operation and the volume of intraoperative bleeding were similar (p = 0.64 and p = 0.165). In conclusion, preincisional infiltration of levobupivacaine is a safe and reliable method for post-tonsillectomy pain reduction in adults. However, more in-depth, double-blinded and placebo controlled studies are required to elucidate its long term benefits.