Aim: The study aimed to investigate cellular expression of IL-17 by CD4+ T-cells in osteoporotic postmenopausal women. Methods: We enrolled 25 postmenopausal women with osteoporosis (PostMO) and 25 postmenopausal women with normal bone mineral density measurements (PostM) to examine the production of IL-17, tumor necrosis factor a (TNFa) and receptor activator of nuclear factor γ-B ligand (RANKL) by CD4+ T-cells and IL-17, RORγt, TNFa and RANKL mRNA levels in CD4+ T-cells. Circulating concentrations of IL-17 along with IL-6, TNFa, RANKL and osteoprotegerin (OPG) were also determined. Results: Osteoporotic postmenopausal women had higher serum concentrations of IL-17 (3.7 ± 1.3 vs. 2.5 ± 1.1 ng/ml, p = 0.042), IL-6 (158 ± 56 vs. 105 ± 39 pg/ml, p = 0.044), TNFa (138 ± 41 vs. 74 ± 11 pg/ml, p < 0.001) and OPG (1.7 ± 0.4 vs. 1.3 ± 0.4 ng/ml, p = 0.039) than healthy controls. The IL-17-producing CD4+ T-cells were higher in the PostMO group than in the PostM group (7.1 ± 2.4 vs. 4.9 ± 1.4%, p = 0.0015). Additionally, osteoporotic postmenopausal women had greater mRNA levels of IL-17 (3.5 ± 2.9 vs. 1.2 ± 1.0%, p = 0.019) and RORγt (5.7 ± 2.5 vs. 2.2 ± 1.0%, p < 0.001) in CD4+ T-cells than in healthy controls. Conclusions: Our findings implied that the upregulated production of IL-17 may play an important role in regulating bone loss in osteoporotic postmenopausal women.