Introduction Long COVID (LC), an often-debilitating infection-associated chronic condition (IACC), affects millions of people globally. Globally, LC patients struggle to access timely, appropriate care, often experiencing disbelief, misunderstandings or being diverted from healthcare. Few studies have examined health system factors influencing LC healthcare access, especially in the Global South. Drawing on the concept of candidacy, we examine health system factors influencing access to LC care in Brazil’s public healthcare system (Sistema Único de Saúde, SUS) and theorise implications for equitable access to public healthcare for IACCs globally. Methods We conducted a patient-engaged, qualitative study in the city of Rio de Janeiro. 29 individual semi-structured interviews were conducted with SUS professionals from administrative leaders to multidisciplinary primary and specialist care staff (November 2022 to July 2023). Verbatim transcripts were analysed using a pragmatic thematic analysis. Results LC patients’ candidacy for care is invisibilised within SUS through multiple, interacting processes. Interplay of an over-burdened health system, prioritisation of resources in response to (flawed) evidence of demand, misalignment of LC patient capacities and demands of navigating fragmented services, complex referral processes, professionals’ lack of LC knowledge and disregard of the severity and morbidity of a chronic condition amid acute demands, led to the under-recognition of LC by healthcare professionals. Professionals’ under-recognition perpetuates administrators’ de-prioritisiation of resources, policies and training necessary to ensure access to appropriate care, creating a cycle of invisibilisation. Conclusion Urgent action to disrupt a cycle of invisibilisation is essential to mitigate patients’ suffering and intensification of inequalities. Disrupting this pernicious cycle requires more than narrow clinical education efforts. Improved surveillance, education, patient involvement, attention to moral injury and building on existing multidisciplinary strengths may enhance access to LC care. Doing so offers wider benefits beyond patients with LC. We call for a paradigm shift in clinical approaches to IACCs.