Fluorescent nanodiamond (FND) has many unique properties, such as photostability and biocompatibility, making it as a novel nanoparticle for both in vitro and in vivo applications. By high energy ion beam irradiation on 100 nm typeIb nanodiamonds and subsequent annealing at high temperature, result in NV0 and NV- defect centers in the diamond crystal lattice which emit far red fluorescence under the excitation of visible light. Excellent optical properties like no photobleaching and no photoblinking along with facile surface fuctionalizabilty and nontoxicity make FND a robust nanoparticle for cell labeling and tracking. Here, we demonstrated that the 100 nm FND as a nanolabel for Hela (adherent cervical cancer cell) and M1 (non-adherent leukemia cell). We introduced FNDs into cells through incubation. Colocalization analysis showed that the internalized FNDs are accumulated in lysosomes with little excretion after 3 hours of post-labeling for Hela cells. Cell division tracking was performed by fluorescence microscopy and cell doubling time was analyzed by flow cytometry. Compared to molecular fluorophore, carboxyfluorescein diacetate succinimidyl ester, FND offers several advantages in long-term cell labeling and tracking. Finally, we demonstrated the long-term in vivo biodistribution of FNDs. FNDs accumulated in liver and spleen after intraperitoneal injection during the study period of 5 months, showing no symptoms of abnormality. The photostability of FND in vivo is also shown here through in vivo imaging system. In conclusion, FND is an ideal nanoparticle for various biological applications.