Sebastes dallii was first formally described as Sebastichthys diploproa in 1890 by the American ichthyologist Charles Henry Gilbert with the type locality given as off Southern California.

[3] Sebastes diploproa is a relatively small stockfish with a deep body a deep-body and large eyes.

Its upper jaw has a distinct incision which separates two tooth-bearing knobs on each side.

[4] Sebastes diploproa Is found in the eastern Pacific Ocean off the western coast of North America from the Alaska Peninsula south to Cedros Island off Baja California.

[1] The pelagic juveniles live underneath floating mats of kelp at the surface[5] settling on the seabed as adults on soft substrates.