Disclosed are a radiation imaging system, an image processing device, a radiation imaging method, and a non-transitory computer-readable recording medium having an image processing program recorded thereon which facilitate the confirmation of a positional relationship between an object of interest and a biopsy needle. In the system using a radiation imaging device as a mammography device, when performing a biopsy of a breast of a subject, the positional relationship is confirmed using a radiation image (projection image) obtained through tomosynthesis imaging. A control unit reconstructs the projection image to generate a tomographic image in a state where the needle is inserted into the breast and generates a reprojection image at a predetermined angle from the tomographic image. The control unit extracts an image of the needle from the projection image, synthesizes the extracted image of the needle into the projection image while aligning, and displays the projection image.