Background: Although Zambia has integrated HIV-self-testing (HIVST) into its Human Immunodeficiency Virus (HIV) regulatory frameworks, few best practices to optimize the use of HIV self-testing to increase testing coverage have been documented. We conducted a prospective case study to understand contextual factors guiding implementation of four HIVST distribution models to inform scale-up in Zambia. Methods: We used the qualitative case study method to explore user and provider experiences with four HIVST distribution models (two secondary distribution models in Antenatal Care (ANC) and Antiretroviral Therapy (ART) clinics, community-led, and workplace) to understand factors influencing HIVST distribution. Participants were purposefully selected based on their participation in HIVST and on their ability to provide rich contextual experience of the distribution models. Data were collected using observations (n = 31), group discussions (n = 10), and in-depth interviews (n = 77). Data were analyzed using the thematic approach and aligned to the four Consolidated Framework for Implementation Research (CFIR) domains. Results: Implementation of the four distribution models was influenced by an interplay of outer and inner setting factors. Inadequate compensation and incentives for distributors may have contributed to distributor attrition in the community-led and workplace HIVST models. Stockouts, experienced at the start of implementation in the secondary-distribution and community-led distribution models often disrupted distribution. The existence of policy and practices aided integration of HIVST in the workplace. External factors complimented internal factors for successful implementation. For instance, despite distributor attrition leading to excessive workload, distributors often multi-tasked to keep up with demand for kits, even though distribution points were geographically widespread in the workplace, and to a less extent in the community-led models. Use of existing communication platforms such as lunchtime and safety meetings to promote and distribute kits, peers to support distributors, reduction in trips by distributors to replenish stocks, increase in monetary incentives and reorganisation of stakeholder roles proved to be good adaptations. Conclusion: HIVST distribution was influenced by a combination of contextual factors in variable ways. Understanding how the factors interacted in real world settings informed adaptations to implementation devised to minimize disruptions to distribution.