Gorgosaurus reached about the size of Albertosaurus and Daspletosaurus. Adult animals grew to between eight and nine meters long and probably weighed more than 2.4 tons. The largest skull found measured 99 centimeters in length, only slightly smaller than that of Daspletosaurus, a tyrannosaurid that lived in the same area at the same time. As with other tyrannosaurids, the skull was large in proportion to the body, with chambers in the skull bones and large skull openings (cranial windows) reducing its weight. Albertosaurus and Gorgosaurus had proportionally longer and flatter skulls than Daspletosaurus and other tyrannosaurids. The end of the snout was blunt and the paired nasal bone (nasale) and paired parietal bone (parietale) were fused, along the midline of the skull, as in all other members of the family. The orbit (orbital window) was round, differing from the oval to keyhole-like shapes in other tyrannosaurids. Similar to Albertosaurus and Daspletosaurus, a high ridge of lacrimal bone extends in front of each eye. Gorgosaurus is distinguished from Albertosaurus by differences in the bones surrounding the brain.
The teeth of Gorgosaurus were typical of all known tyrannosaurids. The eight teeth of the premaxillary at the front end of the snout were small, densely packed, and "D"-shaped in cross-section compared to the rest of the teeth. The remaining teeth were oval in cross-section, rather than blade-shaped as in most other theropods. In addition to the eight teeth of the premaxilla, Gorgosaurus had 26 to 30 teeth in the maxilla and 30 to 34 teeth in the mandible. Gorgosaurus thus has about as many teeth as Albertosaurus and Daspletosaurus, but fewer than Tarbosaurus or Tyrannosaurus.
As with all tyrannosaurids, Gorgosaurus' build plan is characterized by a large head sitting on an "S" shaped neck. In contrast to the large head, the arms were very small. The hands had only two fingers and claws, although a third limb in the metacarpus has been demonstrated in some finds - a rudiment of the third finger as possessed by other theropods. The hind legs of tyrannosaurids were longer in relation to the body than in other theropods. The longest femur known from Gorgosaurus measured 105 centimeters. However, in several smaller specimens, the tibia was longer than the femur - a ratio often found in fast-running animals. The two bones were about the same length in the largest skeletons found.
After the initial description of Yutyrannus in 2012, a large and very closely related species that was fully feathered, it is certain that Gorgosaurus was also clothed in a soft fluff of down feathers.
