There is a fundamental demand for organic fluorescent nanoparticles due to their great significance in the bioimaging field. Herein, we report a facile fabrication of bovine serum albumin nanoparticles loaded with flavonoid dyes via the classic desolvation method. The as-prepared nanoparticles were characterized by fluorescence spectroscopy, dynamic light scattering, scanning electron microscopy, etc. The nanoparticles exhibited several advantages over their counterpart dyes, such as enhanced fluorescent intensity, good photostability, and long-term bioimaging property. This work provided a versatile strategy applying fluorescent dye-loaded biopolymer nanoparticles into bioimaging applications.