Self-assembled peptide amphiphile nanofibers have been investigated for their potential use as in vivo scaffolds for tissue engineering and drug delivery applications. We report here the synthesis of magnetic resonance (MR) active peptide amphiphile molecules that self-assemble into spherical and fiber-like nanostructures, enhancing T(1) relaxation time. This new class of MR contrast agents can potentially be used to combine high-resolution three-dimensional MR fate mapping of tissue-engineered scaffolds with targeting of specific cellular receptors.