The extraction system is a promising environment to prepare nanomaterials with diverse advantages, but its controllability of the size and shape of the products is still relatively weak. Here, CeF3:Tb3+ nanostructures with the morphologies of hollow spheres and nanoplates were controllably prepared using a third phase from an ionic liquid (IL)-based extraction system at an aqueous–organic interface. The shape of the CeF3:Tb3+ nanostructure is controlled from hollow sphere to nanoplate by decreasing the size and amount of the big reverse micelles in the third phase through the addition of iso-propanol. Moreover, the luminescent properties of the as-prepared nanostructures were investigated.