Lucario is a bipedal, canine-like Pokémon, with fur that is predominantly blue and black. It possesses a short, round spike on the back of each forepaw, in addition to a third on its chest. It has a long snout and ears. When its mouth is open, it has two pairs of pointed teeth, one in the upper jaw and one in the lower. It possesses cream-colored fur on its torso, and blue fur on its thighs that resembles shorts. It has a medium length tail of the same blue color as well. It stands on its toes rather than on its entire foot. It has developed four small black appendages on its head, which rise when Lucario reads or manipulates aura, a special energy that it senses. Lucario can study this energy to predict the movements of their opponents and track their quarry. They also have the power to manipulate this energy in an offensive manner, in the form of explosive spheres of energy. Lucario can understand human speech, and have been reported to communicate with humans through telepathy.
As Mega Lucario, its cream fur becomes longer, and its thighs slim down. It develops more spikes on the back of its paws, which have turned crimson. It also develops spikes on both of its feet, which have become crimson too. Its aura-sensing appendages grow longer, and two of them are tipped in crimson. Its shoulders also possess a spike each. Its aura heightens throughout its body, which formed black markings on its blue fur. Mega Lucario was originally believed to be the first discovered Mega Evolution.
Lucario is considered to be prideful, and is extremely loyal to its Trainer. It also seems to have a natural sense of justice. It usually lives deep in mountains very far from people to improve their skills. It is an exceptionally rare Pokémon. Though its diet is unknown, one Lucario was seen eating Berries and plants, like roses. It has been seen eating chocolate, even though chocolate is not part of its natural diet.