Senescent cells accumulate in multiple aging‐associated diseases, and eliminating these cells has recently emerged as a promising therapeutic approach. Here, we take advantage of the high lysosomal β‐galactosidase activity of senescent cells to design a drug delivery system based on the encapsulation of drugs with galacto‐oligosaccharides. We show that gal‐encapsulated fluorophores are preferentially released within senescent cells in mice. In a model of chemotherapy‐induced senescence, gal‐encapsulated cytotoxic drugs target senescent tumor cells and improve tumor xenograft regression in combination with palbociclib. Moreover, in a model of pulmonary fibrosis in mice, gal‐encapsulated cytotoxics target senescent cells, reducing collagen deposition and restoring pulmonary function. Finally, gal‐encapsulation reduces the toxic side effects of the cytotoxic drugs. Drug delivery into senescent cells opens new diagnostic and therapeutic applications for senescence‐associated disorders.

A naphthalimide-based two-photon probe (AHGa) for the detection of cell senescence is designed. The probe contains a naphthalimide core, an l-histidine methyl ester linker, and an acetylated galactose bonded to one of the aromatic nitrogen atoms of the l-histidine through a hydrolyzable N-glycosidic bond. Probe AHGa is transformed into AH in senescent cells resulting in an enhanced fluorescent emission intensity. In vivo detection of senescence is validated in mice bearing tumor xenografts treated with senescence-inducing chemotherapy.