The intervertebral joints (IVJs) of fish were initially viewed as hinges that only allowed lateral flexion, and most studies of their motion and mechanics have focused on 2D flexion during swimming. But in feeding many fish dorsally rotate the neurocranium, elevating it relative to the body to expand the mouth cavity. Cranial elevation requires dorsal flexion of at least the cranio-vertebral joint, and likely some IVJs. It is unknown which IVJs contribute to cranial elevation because dorsal flexion of these joints is challenging to measure. I used X-ray Reconstruction of Moving Morphology (XROMM) to measure 3D motion of the neurocranium and anterior 24 vertebrae in Rainbow Trout, Oncorhynchus mykiss, during feeding (28 strikes, 3 fish). Trout used forward swimming and suction to capture food pellets, with maximum cranial elevation ranging from 2 to 18 degrees (measured as dorsal rotation of the neurocranium relative to a body plane). Lateral flexion was highly variable during cranial elevation, depending on the swimming behavior, and occurred across the IVJs. The vertebral column also flexed dorsally as the neurocranium elevated. Dorsal flexion extended beyond the cranio-vertebral joint as expected, but the magnitude varied across the IVJs. At maximum cranial elevation, the magnitude of dorsal flexion usually increased rostrocaudally over the first 8 IVJs, then decreased to reach a minimum around the 11th postcranial IVJ. Dorsal flexion over the remaining caudal IVJs was variable and usually lower magnitude. Thus, a substantial region of anterior IVJs flexed dorsally and laterally in trout, although not all IVJs appeared to contribute equally to cranial elevation. These data provide a new perspective on the functional and evolutionary morphology of the vertebral column in fish.