Abstract A Zn4L4 type tetrahedral metal-organic cage (MOC-19) was investigated for the host-guest interaction with the anticancer drug Camofur (HCFU) using high-resolution electrospray-ionization mass spectroscopy, UV-Vis spectroscopy titration and NMR spectroscopy. The binding stoichiometry and stability between cage and HCFU was also studied in acetonitrile at room temperature.