Indo-Pacific: Red Sea and South Africa eastward to the Tuamoto and Austral islands, north to the Ryukyu and Hawaiian islands, south to New Caledonia. Eastern Pacific: Costa Rica, Panama and the Galapagos.

Reddish eyes. Color yellowish, densely mottled with dark brown; front of head purplish grey; posterior margins of fins yellow-green; gill opening in a black blotch. Juveniles sometimes bright yellow with brown blotches.

Along drop-offs. Benthic. Occurs in coral or rocky areas of reef flats and protected shorelines to seaward reefs. Feeds on cephalopods fishes, and crustaceans. Most often appears on the reef after a fish has been speared during daylight. The regularity and promptness of such appearances make it clear that G. flavimarginatus is especially sensitive to stimuli emanating from an injured or stressed fish.