Crotalus atrox may be confused with a number of snakes found in Texas, most of which are non-venomous. The majority of these snakes, however, lack the key feature of a rattle found at the end of the tail. Many snakes, including gopher snakes (Pituophis) and hognose snakes (Heterodon) may show an impressive threat display and have similar brown and tan markings, but lack the rattles. Some rattle-less snakes such as rat snakes and copperheads may vibrate their tails.

Like all rattlesnakes, Crotalus atrox has a heat-sensing pit between the eye and nostril. The dorsal markings of rattlesnakes range from the distinct diamond-shaped (rhomboid) marks in Crotalus atrox and the Mojave Rattlesnake (Crotalus scutulatus), to dorsal blotches in the Prairie Rattlesnake (Crotalus viridis) and the Western Massasauga (Sistrurus catenatus), to narrower crossbands extending down the sides of the body in the Rock Rattlesnake (Crotalus lepidus). The pattern of the Western Diamondback is most similar to that of the Mojave Rattlesnake and the Prairie Rattlesnake.

The color of the tail is a useful key to discriminate C. atrox from most other rattlesnakes. In C. atrox, the tail is completely encircled with white and black bands of equal widths. The Mojave Rattlesnake, Crotalus scutulatus, is the only other Texas rattlesnake with such prominent black and white bands around its tail, but the white bands are twice as wide as the black bands.

Crotalus scutulatus does have similar dorsal rhomboid markings running the length of its body, yet these blotches flatten into bands in the posterior third of the body; the diamond markings of C. atrox do not flatten into bands. Adult Mojave Rattlesnakes usually reach lengths of only about three feet, so any very large rattlesnakes are most likely Western Diamondbacks.