Dialga is a dark blue sauropod-like Pokémon with some gray metallic portions, such as its chestplate, which has a diamond in the center. It also has various light blue stripes. It has a fin-like structure on its back and a crest on its head, resembling a dinosaur. Dialga also has two horns on top of its head, two fang-like horns around its mouth, and three spines on the back of its neck. It has three claws on each foot of the same metallic looks as its chestplate. Faint cracks exist across its body. The wing-like structure on its back can be used to focus the flow of time, as seen in Explorers of Time, Darkness, and Sky.
Dialga can warp time by either speeding it up, slowing it down, or stopping it altogether. As Dialga primarily resides in a different dimension, its behavior is nearly impossible to study. It has been shown to be very protective of its home. It also tends to have violent conflicts with its counterpart, Palkia. Dialga is the only known Pokémon that can learn Roar of Time.