Aceclofenac controlled-release (CR) is a once-a-day tablet with 200 mg of aceclofenac, and is bioequivalent to conventional aceclofenac. However, its safety in humans has not been well studied in Korea. Therefore, we aimed to evaluate the overall incidence and patterns of adverse events (AEs), the effectiveness of aceclofenac CR, and the differences in incidence rates of the AEs based on each patient's baseline charateristics. This study was conducted on patients receiving aceclofenac CR in clinical practice at each investigational institution to treat musculoskeletal pain and inflammation. The subjects were administered one tablet of aceclofenac CR (200 mg once-a-day) and were observed for 4 weeks post-administration. Factors affecting the occurrence of AEs were evaluated, and the Visual Analogue Scale (VAS) was used to measure the pain intensity. Among 14,543 subjects, the incidence rate of AEs was 0.86%, and that of adverse drug reactions was 0.74%. No serious AEs and unexpected adverse drug reactions were monitored. The incidence rates of AEs were significantly higher in females, inpatient treatment, individuals with concurrent disorders, and those receiving concomitant medications, respectively (all P < 0.05). Four weeks post-using aceclofenac CR, the mean changes in VAS was significantly decreased compared to prior administration. The overall clinical efficacy rate was 91.63%. This study confirmed that no severe adverse reactions were observed for aceclofenac CR exceeding those previously reported for safety results of conventional formulation of this drug in routine clinical practice settings. The use of aceclofenac CR might not violate the previously reported information on the safety and effectiveness of aceclofenac.