OBJECTIVE To investigate the predictors associated with inadequate adherence in patients receiving proprotein convertase subtilisin/kexin type 9 (PCSK9) monoclonal antibodies (mAbs) in China and to assess the mean LDL-C levels and the percentage reduction of LDL-C. METHODS Patients with at least one PCSK9-mAbs prescription filled between January 2021 and December 2022 were included in this study. The LDL-C levels before and after treatment initiation were assessed using medical records. Adherence to PCSK9-mAbs was assessed for up to 12 months after treatment initiation using the proportion of days covered. RESULTS A total of 415 patients were enrolled. The medication adherence to PCSK9-mAbs after 12 months was 31.8%. A multivariate analysis revealed that better education (junior or high school adjusted OR 2.7 and college or higher adjusted OR 5.2) and LDL-C ＜1.4 mmol/L at 3 months after starting PCSK9-mAbs (adjusted OR 3.0) were consistent predictors of adherence. At 12 months, LDL-C was 1.5mmol/L in the adherence group (mean [SD] decrease, 44.5% [26.5%]) and 1.9 mmol/L in the poor adherence group (mean [SD] decrease, 31.0% [32.7%]), with a group difference of 0.42 mmol/L (group difference in decrease, 13.48%). CONCLUSIONS A better education and LDL-C ＜1.4 mmol/L at 3 months after starting treatment with PCSK9-mAbs were consistent predictors of adherence. In addition, the treatment effect declined more significantly in the poor adherence group over time.