Secret Ballot Protection Act - Amends the National Labor Relations Act to make it an unfair labor practice for: (1) an employer to recognize or bargain collectively with a labor organization that has not been selected by a majority of the employees in a unit appropriate for such purposes in a secret ballot election conducted by the National Labor Relations Board (NLRB), and (2) a labor organization to cause or attempt to cause an employer to recognize or bargain collectively with a representative that has not been selected in such manner.

Requires the NLRB to conduct a secret ballot election to determine whether a labor organization certified or recognized by an employer as the representative to bargain collectively is no longer the representative of a unit (decertification).