Goals of this work quantify repeatability and reproducibility across multiple NIH/NCI Co-Clinical Imaging Research Resources Program (CIRP) preclinical MRI systems in performing diffusion measurement using a standardized acquisition protocol on a shared phantom containing temperature-controlled medium of known diffusivity. To achieve these goals, the CIRP Image Acquisition Data Processing (IADP) working group (WG) performed a round-robin study of an ice water-based DWI phantom using a detailed phantom preparation procedure and standardized DWI acquisition protocol, with both site- and core-lab generated ADC measurements derived from shared datasets.