BackgroundThe World Health Organization has promoted a shift towards the test-and-treat-all strategy to accelerate the elimination of HIV/AIDS. Zambia was one of the early African countries to adopt this strategy as the policy change was officially announced on national television by the republican president on 15th August 2017. This study explored the communication and implementation challenges of the HIV/AIDS policy change to test-and-treat-all in selected public health facilities in Lusaka District, Zambia.MethodsA qualitative case study design was employed with a purposeful sample of policy makers, international partners, National AIDS Council representatives, health facility managers, and frontline health providers in selected tertiary, secondary and primary health facilities in the Lusaka District, Zambia. Thematic data analysis was performed using NVivo 12 Pro software.ResultsIn total, 22 key informant interviews and 3 focus group discussions were conducted. The government relied on formal and informal channels to communicate the test-and-treat-all policy change to health providers. Whilst HIV policy changes were reflected in the National HIV/AIDS Strategic Framework, there was little awareness of this policy by the frontline providers. The use of informal communication channels such as verbal and text instructions affected health providers’ implementation of the test-and-treat-all. Electronic and print media were ineffective in communicating the test-and-treat-all policy change to some sections of the public. Top-down stakeholder engagement, limited health worker training, and poor financing negatively affected the implementation of the test-and-treat-all policy change. Acceptability of the test-and-treat-all policy change was shaped by positive provider perceptions of its benefits, limited sense of policy ownership, and resistance by the non-treatment-ready patients. Furthermore, unintended consequences of the test-and-treat-all policy change on human resources for health and facility infrastructure were reported.ConclusionEffective test-and-treat-all policy change communication is vital for successful policy implementation as it enhances interpretation and adoption among health providers and patients. There is a need to enhance collaboration among policy makers, implementers and the public to develop and apply communication strategies that facilitate the adoption of the test-and-treat-all policy changes to sustain gains in the fight against HIV/AIDS.