Lanthanide complexes have attracted increased attention in recent years for their unique photophysical properties such as large Stokes shifts, narrow bandwidth, long radiative lifetimes, and high luminescence quantum yield. However, low photochemical stability and poor mechanical properties limit the technological applicability of lanthanide complexes. Two natural clay minerals, fibrillar palygorskite (Pal) and tubular halloysite nanotubes (HNTs), are known for their extreme stabilities and high surface area and show promise as new carriers of luminescent lanthanide complexes for further applications. In this report, clay-based lanthanide polymer nanocomposites clay-polyethyleneimine (PEI)-MPTP-Eu(DBM)(3) have been fabricated by attaching a lanthanide complex onto the surface of PEI-modified Pal or HNTs. The formed nanocomposites display visible light-excitable features with a wide excitation wavelength range from UV to visible light, a long luminescence lifetime, and improved photoluminescence stability. Their excellent luminescence, high suspension stability, and low cytotoxicity in cell studies result in the potential applications of the as-prepared nanocomposites for cell imaging in biological systems.