The methods of multimodal imaging are very attractive for a variety of applications in the field of life sciences. Here, we report synthesis of luminescent magnetic nanostructures based on upconversion nanophosphors and superparamagnetic iron oxide nanoparticles for their bimodal detection in vivo. Poly(lactic-co-glycolic acid) copolymer matrix was used for stabilization of nanoparticles in physiological pH and influence of reaction conditions on final size of nanoagents was investigated. The particles were studied by dynamic light scattering and transmission electron microscopy methods. The obtained particles are attractive for biomodal imaging inside small animals in vivo by the methods of optical tomography and magnetic particle quantification methods.