Mandibular third molar surgical extraction, either partially erupted or fully impacted, is the most common surgical procedure in oral and maxillofacial surgery (OMFS). However, this procedure can be associated with many postoperative complications including persistent pain, swelling, trismus, and paresthesia due to nerve injury. This study aimed to identify the correlation of postoperative complications with patient's age, sex, and surgical difficulty level. This study was a cross-sectional retrospective and single-center research conducted on patients with a history of mandibular third molar surgical extraction in the period between 2017 and 2019 at Dental and Oral Hospital Universitas Airlangga, Surabaya, Indonesia. The researchers assessed the factors of age, sex, and surgical difficulty level regarding postoperative complications on the first day of the surgery and after one week on the 7th day of it. Among 916 respondents, the majority of the sample was females (59%) and the dominant age group (60.9%) was the age group of 21-30 years while the dominant surgical difficulty level was shown by the advanced cases group (77%). The statistical analysis showed that there was a significant correlation between surgical difficulty level and postoperative complications including pain, trismus, and paresthesia on the first-day assessment. On the other hand, age was significantly related to complications like pain, swelling, and trismus on the first-week assessment. Age and surgical difficulty level were the most common risk factors of the mandibular third molar extraction postoperative complications. Dentists should take into consideration that older patients (≥51 years) and patients with complex surgical level are more vulnerable to severe postoperative complications.