BACKGROUND: Facility HIV self-testing (HIVST) within outpatient departments can increase HIV testing coverage by facilitating HIVST use in outpatient waiting spaces while clients wait for routine care. Facility HIVST allows for the majority of outpatients to test with minimal health care worker time requirements. However, barriers and facilitators to outpatients' use of facility HIVST are still unknown. METHODS: As part of a cluster randomized trial on facility HIVST in Malawi, we conducted in-depth interviews with 57 adult outpatients (> 15 years) who were exposed to the HIVST intervention and collected observational journals that documented study staff observations from facility waiting spaces where HIVST was implemented. Translated and transcribed data were analyzed using constant comparison analysis in Atlas.ti. RESULTS: Facility HIVST was convenient, fast, and provided autonomy to outpatients. The strategy also had novel facilitators for testing, such as increased motivation to test due to seeing others test, immediate support for HIVST use, and easy access to additional HIV services in the health facility. Barriers to facility HIVST included fear of judgment from others and unwanted status disclosure due to lack of privacy. Desired changes to the intervention included private, separate spaces for kit use and interpretation and increased opportunity for disclosure and post-test counseling. CONCLUSIONS: Facility HIVST was largely acceptable to outpatients in Malawi with novel facilitators that are unique to facility HIVST in OPD waiting spaces. TRIAL REGISTRATION: The parent trial is registered with ClinicalTrials.gov , NCT03271307 , and Pan African Clinical Trials, PACTR201711002697316.