We report a case of multiple myeloma with gastric involvement occurring in a patient who underwent an upper gastrointestinal series (UGIS), CT and MRI. UGIS depicted a luminal protruding mass, while contrast-enhanced CT demonstrated marked thickening of the gastric wall, with subtle contrast enhancement. At T1- and T2-weighted MR imaging, the mass showed iso- and intermediate signal intensity, respectively. After the administration of contrast material, subtle homogeneous enhancement was apparent.