To obtain a CDL, you must be at least: Question To obtain a CDL, you must be at least: Answers 15 years old. 18 years old. 21 years old. 25 years old. Explanation In Pennsylvania, you must be at least 18 years old to obtain a CDL. To operate a commercial vehicle in interstate commerce, you must be at least 21. This questions appears in the following tests: Pennsylvania Class B Knowledge Test
