Polymer‐modified metal–organic frameworks combine the advantages of both soft polymers and crystalline metal–organic frameworks (MOFs). It is a big challenge to develop simple methods for surface modification of MOFs. In this work, MOF@microporous organic polymer (MOP) hybrid nanoparticles (UNP) have been synthesized by epitaxial growth of luminescent boron‐dipyrromethene (BODIPYs)–imine MOPs on the surface of UiO‐MOF seeds, which exhibit low cytotoxicity, smaller size distribution, well‐retained pore integrity, and available functional sites. After folic acid grafting, the enhanced intracellular uptake and bioimaging was validated. Polymer‐modified MOFs: A metal– organic framework@microporous organic polymer (MOF@MOP) composite with low cytotoxicity, smaller size distribution, well‐retained pore integrity, and available functional sites has been synthesized by epitaxial growth of luminescent boron‐dipyrromethene (BODIPYs)–imine MOPs on the surface of UiO‐MOF seeds. After folic acid grafting, the enhanced intracellular uptake and bioimaging was validated (see scheme).