Objectives: Tonsillectomy is a common surgical intervention in otorhinolaryngology. Reported post-tonsillectomy hemorrhage (PTH) rate varies considerably, from 0.5 to 16%. This study was undertaken to analyze the frequency, characteristics, and risk factors of PTH in adults and children undergoing tonsillectomy. Methods: A retrospective analysis was performed of all patients undergoing tonsillectomy for benign indications between January 2008 and May 2014 at the otorhinolaryngology department of Ghent University Hospital. PTH was defined as active bleeding or signs of a recent bleeding from the tonsillar fossa, as observed by a physician. Factors related to patients, medication, and procedure were analyzed for potential risk associations with PTH. Results: Among 957 patients (524 adults. 433 children), 9.2% experienced a PTH (6.6% adults, 2.6% children). In 6.3%. surgical intervention was required to control the bleeding. Whereas the indication for tonsillectomy, season of surgery, peroperative administration of dexamethasone, and per- or postoperative use of non-steroidal anti-inflammatory drugs did not influence PTH rate, significant and independent risk factors for PTH were male sex and being in early and middle adulthood. Conclusions: Hemorrhage following tonsillectomy is not uncommon and leads to revision surgery in a significant number of patients. Male sex and adult age are significant risk factors for postoperative hemorrhage.