We describe the synthesis and characterization of a superparamagnetic nanoobject that consists of a mesoporous iron trimesate-based MOF (i.e., MIL-100(Fe)) whose surface is coated with maghemite nanoparticles. This nano-object combines excellent colloidal stability, low cytotoxicity, and high anti-tumoral activity. It can be used in vivo as an efficient MRI contrast agent because of its excellent relaxivity. All of these properties make this nano-object a potential candidate as a bimodal therapeutic nanovector coupling drug-delivery and MRI properties.