The most notable characteristic in Wei Yan is his speech impairment. He is only able to grunt the most simple of words into phrases. Though seemingly a barbaric, wild beast, he has a kind heart and simply desires to prove his worth. Since his lord sincerely believes in him, he stays loyal to him. However, he isn't the brightest figure in the army and may neglect to consider the consequences of his sometimes rash behavior.

Wei Yan sincerely supports his master, Liu Bei, and seeks to prove his merit as a beast in battle. Since he does not favor words and disobeys instructions, Zhuge Liang keeps a weary eye on him. He commonly causes some form of disobedience during the Battle of Wu Zhang Plains. Wei Yan may defect to Wei during their final battle with Shu at Cheng Du.