Background/Aims: Tuberculosis has incidence and mortality rates that are among the highest for all communicable diseases. Adverse drug reactions (ADRs) to anti-tubercular drugs are common, and have a major impact on treatment maintenance and prognosis. It is important to understand the characteristics of ADRs and establish a suitable management plan. Methods: We retrospectively reviewed patients with ADRs during treatment with first-line antitubercular drugs such as isoniazid, rifampicin, ethambutol, and pyrazinamide from 2009 to 2018. Age, sex, and total treatment period, and the onset, severity, seriousness, and system organ class of ADRs, were analyzed to understand the characteristics of first-line anti-tubercular drug-related ADRs. Results: A total of 1,606 of 5,482 patients (29.3%) experienced ADRs after administration of first-line anti-tubercular drugs. The incidence of ADRs related to isoniazid, rifampicin, ethambutol, and pyrazinamide was 22.2%, 21.3%, 24.5%, and 29.6%, respectively. A total of 2,098 ADR reports were made (mean of 1.3 ± 0.6 per patient). The rates of mild, moderate, and severe ADRs were 32.4%, 61.1%, and 6.5%, respectively. There were 127 reports (6.1%) of serious ADRs. Skin and appendage disorders were most frequently reported (27.5%), followed by gastrointestinal disorders (17.5%), and liver and biliary system disorders (13.1%). The total treatment period was longer in patients who experienced ADRs (224.0 ± 3.1 days vs. 247.0 ± 4.7 days, p = 0.009). Conclusions The incidence of ADRs to first-line anti-tuberculosis drugs was 29.3%, and 6.5% were severe ADRS. ADRs prolonged the overall treatment duration, indicating the importance of their detection and management.