<p>In this paper, the evolving discourse on the preservation of Sharjah’s modern architectural heritage, namely, the structures built during the rapid modernisation of the 1970s and 1980s, is critically examined. The tension between museumification, in which buildings are treated as static, curated historical relics, and performative reuse, in which the activation of sites is advocated through new, evolving functions and continuous social engagement, is investigated in this study. This research takes a qualitative case study approach, analysing three emblematic sites in Sharjah, namely, Al Qasimiyah School, the Flying Saucer, and Bank Street, as some of the first adaptive reuse projects developed in Sharjah. Taking a perspective informed by critical heritage studies, the paper introduces a new adaptive authenticity conceptual framework, proposing that, even as its physical space is modified or repurposed, a site’s significance can be maintained through the continuity of cultural practice and narrative. Performative adaptive reuse is found to be a more sustainable, culturally dynamic, and inclusive pathway for modern heritage in the Gulf. Modern structures can be repositioned through the embracing of adaptive authenticity, not as relics but rather as active, vital components of urban life, thereby ensuring that heritage remains a living, evolving resource for the community.</p>