BACKGROUND: Instruments that measure the patient-reported outcome and quality of life are essential to assess the treatment success of any medical intervention. This review represents valid and reliable outcome assessment instruments for tonsillectomy (TE) and tonsillotomy (TO) in adult patients as TE/TO still belong to one of the most common performed surgical procedures. METHODS: A systematic review of the literature in the MEDLINE, PubMed, Web of Science and Cochrane Library was conducted. Studies describing reliable and valid patient-reported outcome measures (PROM) in adults with regard to the perioperative as well as postoperative follow-up after TE/TO were examined. Thus, studies without PROMs or PROMs only relating to children as well as studies in non-English/non-German language or without any detailed information were excluded. RESULTS: Four thousand four hundred forty studies were identified. Thirteen reliable and valid patient–reported outcome assessment instruments presenting the perioperative and postoperative outcome were analysed. Four generic questionnaires are included that are used to measure the outcome after TE/TO in adults. Four disease-specific questionnaires relating to obstructive sleep apnea (OSA) and sleep disordered breathing (SDB) as well as two TE/TO specific questionnaires are validated for adults. With regard to the perioperative outcome including parameters like pain, nausea, vomiting, satisfaction three assessment instruments are analysed. CONCLUSION: This review describes the currently available, reliable and valid generic and disease-specific instruments assessing the perioperative as well as postoperative outcome to evaluate the treatment success after TE/TO in adult patients. Therefore, this study improves the selection of the appropriate patient–reported outcome assessment instrument to assess the quality of life in adults undergoing TE/TO.