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.