Significant advances in our understanding and treatment of HIV have led to improvements in the medical management of the illness, as HIV infection has evolved from an acute to a chronic illness. Increasing our understanding of the medical and/or psychosocial comorbidities, which can interact to determine "clinical complexity" and impact HIV management, will further strengthen this process. Retention in care is a critical step of the HIV Treatment Cascade, which facilitates effective management of these comorbidities and their impact on HIV medical management. This study sought to build on literature regarding medical and/or psychosocial comorbidity that impacts retention in care, and it often leads to clinically complex presentations, by gaining the perspectives of people living with HIV (PLHIV), and medical and allied health clinicians in the field in Sydney, Australia. A total of 16 clinicians (medical doctors, nurses, clinical psychologists, and social workers) and 14 clients participated in a series of focus groups; they were asked to comment on the perceived barriers to retention and the potential solutions to overcome these. The results indicated a significant degree of overlap between clinician and client perspectives, and they identified "service-specific factors," "logistic/practical factors," "medical/physical factors," and "psychosocial factors" as potential barriers to retention. Results are reviewed in the context of similarities and differences in perspectives between clinicians and PLHIV, and limitations regarding the generalizability of findings are discussed. The broader context of comorbidity and clinical complexity is also examined.