There is no definitive answer to this question, as it depends on a number of factors such as the individual's strength, swimming ability, and experience. However, most experts agree that children as young as five or six years old can safely start paddle boarding with adult supervision. For younger children, it is important to choose a board that is specifically designed for their smaller size and weight. Also, always ensure that your child wears a life jacket and has someone nearby who can assist if needed.