Swiftopecten swifti has a shell reachinga size of, with a maximum of. The shell is fan-shaped and it is composed of two valves, each of which is convex and has a few broad ribs. These radiate from the umbo, the rounded protuberance near the hinge. Beside the hinge are two irregular shell flaps or auricles with the anterior one normally being much larger than the other. This provides an attachment for the single strong adductor muscle that closes the shell. The backgroundcolour varies from pale brown to pale purple. These scallops can live up to 13 years. They are filter feeders, sieving microscopic algae from water that passes through its gills.