The combination of magnetic resonance imaging (MRI) and fluorescent imaging with a dual-modal probe could exert the advantages of the two imaging techniques, simultaneously achieving high spatial resolution and sensitivity in tumor diagnosis. Herein, a magnetic and fluorescent dual-modal nanoprobe of ca. 8 nm was prepared through self-assembly of a star-like polymer comprising of porphyrin core, gadolinium chelate and solubilizing PEG. The probe did not show photodynamic therapy capability, but displayed strong red fluorescence with two emission peaks at 650 nm and 710 nm when excited at 585 nm, and the relaxation experiment indicated the probe had a longitudinal relaxivity (r(1)) of 7.1 mM(-1) s(-1), 1.6 times higher than that of small molecule contrast agent DTPA-Gd3+. The in vivo MRI and ex vivo fluorescent imaging experiments indicated that the probe had excellent tumor-targeting capability and could effectively delineate the boundary of tumor. (C) 2016 Elsevier Ltd. All rights reserved.