We synthesized biocompatible and stable fluorescent carbon dot probe from a natural source, Curcuma longa. The fluorescent nanoparticles (C-FNPs) derived from carbonization process showed multi-color fluorescence emissions which had small particle size (~17 nm) and were water-soluble. The surface passivated with polyethylene glycol (PEG) capped with amine groups in FNPs (P-FNPs) generated a sensor with higher quantum yield and longer fluorescence lifetime than obtained with C-FNPs. Furthermore, the prepared material showed an excellent biocompatibility with almost 100% cell viability, even at high concentrations of materials. Due to their stability and small size in water, this system offers a potential method to generate a novel cell imaging agent. Therefore, fluorescence sensors from natural sources may be useful for numerous biomedical research applications.