In 85% of Ewing family tumors, the NH₂ terminus of EWS is fused to the DNA-binding domain of FLI1, an ets transcription factor. The resulting chimeric protein is a strong transcriptional activator with transforming activity. We report that EWS and EWS-FLI1 interact via their common NH₂ terminus with the COOH terminus of BARD1, a putative tumor suppressor, in vitro and in vivo. Because BARD1 associates via its NH₂-terminal RING domain with the breast cancer susceptibility gene BRCA1 that provides a platform for interactions with proteins involved in DNA repair and checkpoint control, our results provide a link between the Ewing’s sarcoma gene product and the genome surveillance complex.