Present study evaluated effects of addition of Nanoparticles fluorapatite (Nano-FA) on microhardness and fluoride release of a Glass Ionomer Cement (GIC, Fuji IX GP Fast). Forty-eight specimens prepared, divided equally into 4 groups (2 with Nano-FA); after 24 h and one week Vickers microhardness (HV) was measured. Nano-FA specimens were made from addition of nano-FA to Fuji IX powder (glass powder/Nano-FA ratio=20:1 wt/wt, 3.6:1 P/L ratio). At 24 h, mean (95% CI) HV for GIC and Nano-FA GIC were 40.59 (39.51-41.66) and 46.89 (45.95-47.82) kg/mm2, and at one week 44.98 (44.23-45.72), 53.29 (52.58-53.99) kg/mm2, respectively. Findings indicated higher HV in Nano-FA specimens (F=221.088, p<0.001). Twenty-eight days weekly cumulative fluoride release in both groups was not different (p>0.05). MTT assay exhibited no inhibition of cell proliferation or reduction in metabolic activity in experimental [84.0 (3.3)] or control groups [85.1 (4.7)] with no difference between groups (p>0.05). New nano-FA GIC was biocompatible and showed improved surface hardness. Future clinical trials can verify the usefulness of Nano-FA GIC.