Objectives: Osteoporosis is a common complication in patients undergoing long-term corticosteroid therapy, particularly those with rheumatological and immunological conditions. Denosumab has shown potential in enhancing bone density and reducing fracture risk in such patients. This study evaluates the effectiveness of denosumab in osteoporosis management among corticosteroid-treated individuals. Methods: Between 2013 and 2022, 390 osteoporosis patients who received denosumab (60 mg subcutaneously every 6 months) for ≤18 months were enrolled. Patients were categorized based on corticosteroid use, and age-matching was applied to ensure comparability. Bone mineral density (BMD) and trabecular bone score (TBS) at the lumbar spine and femoral neck were assessed, and secondary fractures during the follow-up period were recorded. Results: Over the 18-month follow-up, both groups showed improvements in lumbar spine T-scores. The corticosteroid group increased from −2.1 ± 1.2 to −2.0 ± 1.3 (p < 0.001), while the non-corticosteroid group improved from −2.6 ± 1.2 to −2.4 ± 1.2 (p = 0.003). However, logistic regression analysis revealed that corticosteroid use remained a significant risk factor for secondary fractures (odds ratio: 1.69; 95% confidence interval: 1.11–2.56, p = 0.014), despite denosumab treatment. Conclusions: This retrospective study observed stabilization and a modest increase in BMD and TBS among corticosteroid users. Although differences in secondary fractures persisted between groups, denosumab shows potential for managing corticosteroid-induced osteoporosis. The study’s focus on Taiwanese patients limits its generalizability, and future research should include diverse populations to enhance applicability.