Summary What is known and objective Higher rate of statin‐related hepatotoxicity has been reported for Koreans than for Westerners. Moreover, statin‐related aminotransferase elevation for those who show borderline levels of aspartate transaminase (AST) and alanine transaminase (ALT) (≤×3 of UNL) at baseline has not been fully investigated. Methods Post‐statin changes AST/ALT levels during the first year for 21 233 Korean outpatients at two large academic teaching hospitals from January 2009 to December 2013 were analysed using electronic health record data. The date of the first statin prescription was set as baseline. We also performed a comparative analysis of statin‐related AST/ALT elevations according to the type of statin, followed by an analysis of clinical risk factors. Results and discussion The progression rate to abnormal AST/ALT values >×3 the upper normal limit (UNL) was significantly higher (2·4–16% vs. 0·3–1·7%, P < 0·001) in subjects with borderline (>×1, but ≤×3 of UNL) compared with normal AST/ALT values at baseline. Those with normal baseline AST/ALT did not show significantly different progression rate between different statin medications (P = 0·801). However, patients taking pitavastatin (HR = 0·76, P = 0·657) were least likely to develop abnormal AST/ALT, whereas those taking fluvastatin (HR = 2·96, P = 0·029) were the most likely to develop abnormal AST/ALT compared with atorvastatin for patients who were with baseline borderline AST/ALT. However, given the small sample sizes and the observational nature of our study, these need further study. What is new and conclusion It is advisable to regularly monitor AST/ALT levels even in patients with AST/ALT increases >×1. Future studies should aim to determine the possible risk factors for each specific statin type by analysing various confounding variables. The progression rate to abnormal AST/ALT values (>×3 the UNL) was significantly higher in subjects with borderline (>×1, but ≤ ×3 of UNL) compared to normal AST/ALT values at baseline. It is advisable to regularly monitor AST/ALT levels in patients with AST/ALT increases >×1, but ≤×3 of UNL.