Preclinical cancer models are invaluable for studying oncogenic pathways and assessing therapies. However, precise detection of small tumours with specificity, sensitivity and high resolution remains challenging. A member of the Organic Anion Transporting Polypeptide 1 (OATP1) family of proteins, called OATP1A1, can take up the clinically-approved, liver-specific paramagnetic agent Gd-EOB-DTPA. Significant increases in spin-lattice relaxation rates were exhibited at 3T by triple negative breast cancer (TNBC) cells engineered to express OATP1A1 and pilot data showed enhancement of OATP1A1-expressing orthotopic TNBC tumours in mice. Our data supports the utility of OATP1A1 for improved MR detection of TNBC tumours in animal models.