INTRODUCTION: Multimodal imaging agent has the potential to overcome the shortage and incorporate the advantages of different imaging tools for extremely sensitive diagnosis. To achieve multimodal imaging, combining multiple contrast agents into a special nanostructure has become a main strategy; However, the combination of all of these functions into one nanoplatform usually requires a complicated synthetic procedure that results in heterogeneous nanostructure. METHODS: In this study, we develop ultrasmall gold nanoclusters with 15 gold atoms (AuNCs) functionalized with diethylenetriamine-pentaacetic acid dianhydride (DTPAA-Gd) as an optimized multimodal imaging agent to enhance imaging ability. RESULTS: The AuNCs-DTPAA-Gd nanohybrids possess the ultra-small size and are capable of enhancing the contrast in near-infrared fluorescence (NIRF), magnetic resonance (MR) and X-ray computed tomography (CT) imaging. Meanwhile, the integrated DTPAA-Gd component not only endow the nanohybrids to produce higher T relaxivity (r = 21.4 mM s) than Omnipaque (r = 3.973 mMs) but also further enhance X-ray attenuation property of AuNCs. Importantly, the fluorescence intensity of AuNCs-DTPAA-Gd did not decrease compared with AuNCs. Ultimately, in vivo imaging experiments have demonstrated that AuNCs-DTPAA-Gd nanohybrids can be quickly eliminated from the body through the urinary system and has great potential for anatomical imaging. CONCLUSION: These data manifest AuNCs-DTPAA-Gd present great potential as a multimodal contrast agent for disease diagnosis, especially for early accurate detection of tumors.