To assess the efficacies and potential predictors of a corticosteroid switch in metastatic castration-resistant prostate cancer (mCRPC) patients with biochemical progression on abiraterone acetate plus prednisone (A + P).Patients with mCRPC treated between April 2016 and August 2020, who experienced biochemical progression on A + P and then switched to A plus dexamethasone (D), were retrospectively identified. The primary endpoint was progression-free survival (PFS), and the secondary endpoints were PSA response, overall survival (OS), and safety.One hundred and thirty consecutive cases were enrolled. The median PFS and OS on A + D were 5.0 and 18.7 months, respectively. The best PSA decline of ≥50% (PSA50) and ≥ 30% (PSA30) were observed in 29.2 and 46.2% patients, respectively. Lower PSA at corticosteroid switch (≤ 20 ng/mL; median PFS, HR 0.63, p = 0.019; median OS, HR 0.38, p = 0.001) and longer mCRPC-free survival (≥ 18 months; median PFS, HR 0.61, p = 0.013; median OS, HR 0.51, p = 0.015) were identified as independent prognostic predictors associated with longer PFS and OS. A risk stratification tool was developed to select candidates for corticosteroid switch based on the independent prognostic predictors of PFS and OS.A corticosteroid switch from prednisone to dexamethasone is effective for mCRPC which progressed on A + P treatment. Patients with lower PSA at corticosteroid switch and/or longer mCRPC-free survival may gain more benefits by the corticosteroid switch.© 2021. The Author(s).