Bone metastases are frequently observed in patients with certain types of cancer and are significant cause of morbidity. Zoledronic acid (ZA) is routinely prescribed for patients with bone metastases by affecting osteoclast function. We aimed to assess the effect of ZA over time in patients with bone metastases by analyzing novel bone turnover marker levels including receptor activator of nuclear factor-k B ligand (RANKL) and osteoprotegerin (OPG) in serum and gingival crevicular fluid (GCF). Also, associations between these bone turnover markers with hematological and biochemistry dysregulation were studied. The study enrolled patients with bone metastases including 32 patients diagnosed with solid tumors and 15 patients with multiple myeloma. In these patients, GCF and serum RANKL and OPG levels were measured and compared with measures of hematological and biochemical parameters before and after 3 months of ZA therapy. Mean subject age was 54 years old with a range of 28-80 years. Skeletal-related events were observed in 8.5 % of all patients. After the 3-month treatment of ZA therapy, no significant differences were found in serum and GCF levels of RANKL and OPG when compared with before treatment levels. GCF RANKL levels at baseline and following 3 months of ZA therapy were significantly higher in patients with solid tumors when compared patients diagnosed with multiple myeloma (p = 0.001; p < 0.001, respectively). GCF OPG levels after the entire course of ZA therapy were greater in patients with 5 or more bone metastases (p = 0.04). For patients with multiple myeloma, control GCF OPG was negatively correlated with control platelet and WBC counts (p = 0.018 and p = 0.027, respectively). A negative correlation was observed between control serum RANKL and control serum OPG levels in myeloma patients (p = 0.001). After 3 months of ZA therapy, no significant differences were observed in GCF and serum RANKL and OPG levels when compared with baseline. A negative correlation was observed between serum control RANKL and OPG levels in myeloma patients. OPG levels were greater in patients with 5 or more bone metastases. In patients diagnosed with multiple myeloma, GCF OPG levels were negatively associated with WBC and platelet counts.