Lanthanide-based single-molecule magnets (SMMs) have captivated the attention of researchers due to their great potential application in quantum information processing, storage, spintronics etc. Recent years have witnessed continuous breakthroughs in the field of SMMs, which make them very promising to be used in future practical functional applications. However, there remain formidable obstacles involving suppression of the quantum tunneling of magnetization (QTM) to maximize magnetic anisotropy, integrating and applying them in devices etc. Meanwhile, multifunctional 4f-based SMMs, which combine optical and electronic properties, are attracting increasing attention. This will provide a new perspective for future multifunctional device applications and deep insight into understanding the magnetic relaxation behavior as well. In this frontier article, we highlight the research that recently emerged involving 4f-based SMMs in combination with luminescence thermometry and photochromic and ferroelectric properties, respectively.