The objective of this study is to design and develop a green-synthetic, multifunctional hybrid micelles with shell embedded magnetic nanoparticles for theranostic applications.The hybrid micelles were engineered based on complex micelles self-assembled from amphiphilic block copolymers Pluronic F127 and peptide-amphiphile (PA) pal-AAAAHHHD.The reason to choose PA is due to its amphiphilic character and the coordination capability for Fe3+ and Fe2+.The PA incorporation allows the in situ growth of the magnetic iron oxide nanoparticles onto the complex micelles, to yield the nanostructures with shell embedded magnetic nanoparticles at an ambient condition without any organic solvents.The anticancer drug doxorubicin (DOX) can be efficiently loaded into the hybrid micelles.Interestingly, the magnetic nanoparticles anchored on the shell were found to significantly retard the DOX release behavior of the drug loaded hybrid micelles.It was proposed that a cross-linking effect of the shell by magnetic nanoparticles is a key to underlie the above intriguing phenomenon, which could enhance the stability and control the drug diffusion of the hybrid micelles.Importantly, in vitro and in vivo magnetic resonance imaging (MRI) revealed the potential of these hybrid micelles to be served as a T2-weighted MR imaging contrast enhancer with improved performance.