In patients with systemic lupus erythematosus (SLE), neuropsychiatric (NP) symptoms sometimes occur after administration of corticosteroids, making differential diagnosis between NPSLE and steroid-induced psychosis challenging for clinicians. The aim of this study was to clarify the characteristics of post-steroid NP disease (PSNP) in patients with SLE. Clinical courses of 146 patients with SLE and 162 with other systemic autoimmune diseases, all in the absence of NP manifestations on admission, were retrospectively analyzed. Forty-three NPSLE patients on admission (de novo NPSLE) were also investigated. All patients were consecutively recruited and treated with 40mg/day or more of prednisolone in Hokkaido University Hospital between April 2002 and March 2015. The prevalence of PSNP was strikingly higher in SLE patients than other systemic autoimmune diseases (24.7% vs. 7.4%, OR 4.09, 95% CI 2.04-8.22). As independent risk factors to develop PSNP in SLE patients, past history of mental disorder and the presence of antiphospholipid syndrome were identified using multiple logistic regression analysis. In patients with PSNP-SLE, mood disorder was significantly more frequent than in de novo NPSLE (47.2% vs. 20.9%, OR 3.38, 95% CI 1.26-9.04). Of PSNP-SLE patients, two-thirds were with one or more abnormal findings in cerebrospinal fluid, electroencephalogram, MRI or SPECT. Majority of our PSNP-SLE patients received intensified immunosuppressive treatments and experienced improvement in most cases. PSNP-SLE had better relapse-free survival than de novo NPSLE (p<0.05, log rank test). In conclusion, PSNP frequently occurred in patients with SLE and treated successfully with immunosuppressive therapy, indicating that NPSLE is likely to harbor patients with PSNP-SLE.