Polymer-based nanosystems have been extensively explored either as therapeutic agents or bioimaging probes in the cancer diagnosis. However, very few systems are successful in combining both therapy and imaging. Herein, a new class of norbornene based copolymer, Nor-Dox-Cob-Btn is proposed as potential theranostics agent for tumor diagonosis. The copolymer (Nor-Dox-Cob-Btn) with doxorubicin, cobalt carbonyl complex, and biotin as pendent functionalized group is synthesized, using ring opening metathesis polymerization (ROMP). The cell viability, drug release, NMR relaxation, NMR 1-D image and Epi fluorescence microscopy studies on Nor-Dox-Cob-Btn nanocarrier are thoroughly studied. The effect of nanocarrier on transverse relaxation (T-2) of water molecule and NMR 1-D image suggest that the nanocarrier has the potential application in magnetic resonance imaging agent. The T-2-weighted MRI agent, along with biotin receptor assisted pH responsive doxorubicin release from Nor-Dox-Cob-Btn, prompts us to envision this newly developed polymer for future application in theranostics.