Micromixer technology was used to prepare polymeric vesicles (Pluronic® L-121) dual loaded with the anti-cancer drug camptothecin and magnetic nanoparticles. Successful incorporation of the magnetic nanoparticles was confirmed by transmission electron microscopy. Dynamic light scattering measurements showed a relatively narrow size distribution of the hybrid polymersomes. Camptothecin polymersomes reduced the cell viability of prostate cancer cells (PC-3) measured after 72 h significantly, while drug-free polymersomes showed no cytotoxic effects. Covalent attachment of a cancer targeting peptide (bombesin) as well as a fluorescent label (Alexa Fluor® 647) to the hybrid polymersomes was performed and specific cell binding and internalization were shown by flow cytometry and confocal microscopy. Relaxometry measurements clearly demonstrated the capacity of magnetic polymersomes to generate significant T2-weighted MRI contrast and potentially allow for direct monitoring of the biodistribution of the polymersomes. Micromixer technology as an easy, fast and efficient way to manufacture hybrid polymersomes as theranostic drug delivery devices is a further step from basic research to personalized medicine. © 2013 The Royal Society of Chemistry.