Protecting Older Workers Against Discrimination Act This bill amends the Age Discrimination in Employoment Act of 1967 to establish an unlawful employment practice when the complaining party demonstrates that age or participation in investigations, proceedings, or litigation under such Act was a motivating factor for any unlawful employment practice, even though other factors also motivated the practice (thereby allowing what are commonly known as "mixed motive" claims). The bill (1) permits a complaining party to rely on any type or form of admissible evidence, which need only be sufficient for a reasonable trier of fact to find that an unlawful practice occurred; and (2) declares that a complaining party shall not be required to demonstrate that age or retaliation was the sole cause of the employment practice (thereby rejecting the Supreme Court's decision in Gross v. FBL Financial Services, Inc., which requires a complainant to prove that age was the "but-for" cause for the employer's decision). The bill authorizes a court in a claim in which age discrimination is shown to grant declaratory and injunctive relief, but prohibits a court from awarding damages or issuing an order requiring any admission, reinstatement, hiring, promotion, or payment. The bill applies the same standard of proof to other employment discrimination and retaliation claims, including claims under the Civil Rights Act of 1964, the Americans With Disabilities Act of 1990, and the Rehabilitation Act of 1973.