To obtain a hazardous materials endorsement on a CDL, an applicant must be at least: Question To obtain a hazardous materials endorsement on a CDL, an applicant must be at least: Answers 18 years old. 21 years old. 23 years old. 25 years old. Explanation An applicant must be at least 21 years old to obtain a CDL with a HazMat endorsement.