We analyzed 11 patients with multiple myeloma (MM) treated using denosumab in our institute. The median age was 69 years (range, 54-76 years), and 7 patients were male. Seven patients had presented with newly diagnosed MM. Four patients were initially treated with zoledronic acid, which was then later switched to denosumab. The median number of injections was 15 (range, 1-27). No patients developed skeletal-related events (SRE) during denosumab treatment. Hypocalcemia was defined as serum calcium levels below the baseline in all patients. To prevent hypocalcemia, 8 patients were administered oral calcium. The first course of denosumab injections in 9 patients resulted in more marked decreases in serum calcium concentrations than subsequent courses. Two patients discontinued denosumab after osteonecrosis of the jaw (ONJ) was suspected, but squamous cell carcinoma was later identified in one of these cases. Denosumab might be effective and safe for preventing SRE. Cautionary measurement of serum calcium concentrations and prophylactic supplementation with oral calcium are warranted to avoid hypocalcemia after the first denosumab injection. The possibility of ONJ also merits attention. The clinical diagnosis of ONJ should be considered based on performing appropriate histological analyses.