The combination of fluorescent and magnetic properties in single nanosystems is of current interest for applications in the biomedical and biological sciences, including drug delivery, and cell separation and labelling procedures. These nanocomposite particles are generally synthesised using high-temperature procedures, and many involve encapsulation in a silica or polymer coating. The resulting large particle size may limit the use of these nanocomposites in biological work. We demonstrate an aqueous self-assembly route to fabricate nanohybrids combining cadmium telluride quantum dots and magnetite nanoparticles. The entire procedure is conducted under aqueous conditions to improve sustainability and physiological compatibility. The resulting nanocomposite displays strong fluorescent emission, and superparamagnetic behaviour.