A marker delivery device, “adaptor”, for a MRI breast biopsy system is described and claimed. The marker adaptor for the MRI breast biopsy device provides the operator with the ability to easily mark after an MRI biopsy procedure through the biopsy sleeve. The flexible shaft marker snaps into the marking adaptor which creates the oval shape that mates with the inner surface of the sleeve. This locks the orientation of the sleeve and marker, with adaptor, together. The marker adaptor also contains a hard-stop which allows the user to place the biopsy marker in the correct location.