Selective deposition of Gd(III) ions onto the shell structure of complex micelles was achieved to yield Gd decorated hybrid micelles for integrated magnetic resonance imaging and drug delivery. The complex micelles were engineered by the hydrophilic–hydrophobic self-assembly of two kinds of amphiphilic polymers, pluronic F127 and a peptide-amphiphile (PA), via a facile, environmentally benign strategy. These core–shell complex micelles provide a robust multifunctional platform for theranostic applications. The hydrophobic core of micelles allows us to compartmentalize anti-cancer drugs, while the shell structure with a mixed poly(ethylene-oxide) (PEO) and peptide composition provides chelation capacity for the MRI contrast agent Gd(III). The nanoscaled hybrid micelles are not only developed to address the challenges of small molecular Gd(III)-chelates, but also be integrated with the capability of anticancer drug delivery for tumor therapy. More importantly, a synergy effect was observed such that the coordination effect of Gd(III) with the shell enhanced the micellar stability and retarded the DOX release behavior. In vitro and in vivo experiments of MRI contrast enhancement and therapy clearly evidenced that the DOX loaded hybrid micelles can serve as efficient theranostic agents.