This study investigated the suitability of a Gd(3+)-containing polymer complex used as a magnetic resonance (MR) signal-enhancing coating material. The synthesis of the Gd>(3+)-containing polymer complex was done by conjugating N-(2-hydroxyethyl)ethylenediaminetriacetic acid (HEDTA) with poly (styrene-maleic acid) copolymer (SMA), followed by coordinating with Gd(3+). The characterizations of FT-IR, NMR and XPS confirmed that HEDTA was covalently attached to SMA and Gd(3+)-containing polymer complex was formed. Coating such Gd(3+)-containing polymer complex on the surface of polypropylene (PP) catheter was performed by solution coating method. The results of MR imaging experiments in vitro indicated that the PP catheter coated with this coating material showed strong MR signal in the vicinity of the catheter surface and a clear contrast between the catheter surface and background. Based on these results, a novel MR signal-enhancing coating material, which showed the great potentialities in making catheters for endovascular intervention, visible by MR imaging, can be developed.