Although we know that authenticity work can add value to cultural products, little research explores efforts to claim the inauthenticity of products in commercial markets. The question arises, how does the critical reception of a popular culture phenomenon employ a form of authenticity work to determine the cultural products eligible – or ineligible – for the status of "authentic?" This research seeks to answer this question through a comprehensive content analysis of 328 documents from 1998 to 2012 related to the late artist Thomas Kinkade. We put forth the term inauthenticity work to explain how cultural intermediaries defined cultural products as antithetical to authenticity. Even in the face of immense commercial success, intermediaries constructed Kinkade’s work as exemplifying inauthenticity, defining his work as mass produced, insincere, escapist, and oppositional to high art. Such inauthenticity work reveals that even if there is greater variance in cultural products eligible for authentication, intermediaries uphold culture boundaries through critically maintaining a cultural realm of inauthenticity.