Provided herein are PD-L1 antibodies and methods for using the same for diagnosing a medical condition associated with elevated PD-L1 levels (e.g., cancer) in subjects in need thereof and antigen binding fragments thereof. The PD-L1 antibodies and antigen binding fragments are also useful in evaluating the efficacy of a particular therapeutic regime in a subject diagnosed as having a PD-L1-related medical condition.