Fluorescent epoxy nanocomposites reinforced with polydopamine (PDA) functionalized zinc oxide (ZnO) nanoparticles have been obtained. Results reveal that the PDA functionalized ZnO nanoparticles are dispersed uniformly in the epoxy nanocomposites. The enhanced tensile strength of the epoxy nanocomposites filled with PDA functionalized ZnO nanoparticles (up to 106.7 MPa) is obtained compared with that of pure epoxy (83.8 MPa) and epoxy nanocomposites filled with the same loading pristine ZnO nanoparticles (around 91.5 MPa). The glass transition temperature (T_g) of the epoxy nanocomposites filled with PDA functionalized ZnO nanoparticles has shifted to a higher temperature (127.0–132.0 °C) compared with that of pure epoxy (118.3 °C). The interaction between PDA and epoxy matrix is also explored by Fourier transform infrared (FTIR) and contact angle. The introduction of PDA can enhance the mechanical and thermal properties of epoxy nanocomposites without damaging the fluorescent property of ZnO nanoparticles.