Sonic's demeanour is always easygoing, cool and carefree. However, he is often impatient, hates boredom, and possesses at times a short temper. Because of his impulsive nature, Sonic can be reckless and quick to act before thinking, throwing himself into trouble without a second thought and regards for others' warnings. Nevertheless, he is honest and always keeps his promises.

Sonic's personality is a juxtaposition of kindness and ferocity. He is extremely benevolent, driven by his own strong sense of justice and fair play, and firmly stands for truth and freedom. However, he is never the one to rest in the face of injustice or oppression. He hates lies and evil in all its forms, exploding with anger when witnessing anything unjust, and will do all he can to snuff it out, throwing his life on the line without hesitation. However, he usually sees his heroics as an opportunity to have fun, making him a thrill-seeker. To Sonic, saving the world is no big feat and just another thrilling episode in his life. When he finds himself in a pinch, he acts as though nothing can stop him. In times of crisis, though, he is aggressive and focuses intensely on the task at hand as if his personality has undergone an astonishing change. At the same time, Sonic has a big and kind heart and is fully committed to helping out anyone in need at any time, even if it means getting himself into trouble or being despised by others.