Whilst progress has been made, evidence of effective approaches to improve action on addressing the social and structural drivers of the HIV epidemic remains a priority, to meet the 2030 sustainable development agenda, and to achieve key HIV targets, including the 90-90-90 target and the Treatment as Prevention (TasP) intervention. With a focus on the public sector in South Africa, we critically reflect on the HIV mainstreaming approach, assessing its ability to augment multisectoral action on the response to HIV. We reflect on progress made in mainstreaming HIV in non-health sector departments, exploring factors that have enabled and hindered the process. We also highlight limitations in the adopted approach to mainstreaming HIV in non-health sector departments in South Africa; which currently promotes working in silos and does not encourage collaboration and partnerships. We propose a three-step approach to effective mainstreaming of HIV that will augment multisectoral action. The approach also contributes towards realising the sustainable development agenda of "leaving no one behind" and achieving the national and global targets on HIV that are embedded in collaborative efforts.