To apply for a CDL, you must be at least: Question To apply for a CDL, you must be at least: Answers 15 years old. 18 years old. 21 years old. 25 years old. Explanation You must be at least 18 years old to apply for a CDL. However, you must be at least 21 years old to drive in interstate commerce, as well as to have a hazardous materials, passenger, or school bus endorsement.
