The main causes of children’s slurred speech include the following: 1. caused by children just learning to speak. When children first learn to speak, their pronunciation is not clear and they may have temporary slurred speech. 2. If a child has congenital dysfunction, it will cause slurred speech and motor and developmental delays. 3. If a child has serious brain damage, such as severe encephalitis or severe cerebral palsy, slurred speech will also occur.