In sub-Saharan Africa, most new HIV infections occur in stable relationships, making couples testing an important intervention for HIV prevention. We explored factors shaping the decision-making of cohabiting couples who opted to self-test in Blantyre, Malawi. Thirty-four self-tested participants (17 couples) were interviewed. Motivators for HIV self-testing (HIVST) emerged at three main levels. Individual motivations included perceived benefits of access to treatment, and self-checking of serostatus in the hope of having been cured by prolonged treatment or faith-healing. HIVST was considered convenient, confidential, reassuring and an enabling new way to test with one's partner. Partnership motivations included both positive (mutual encouragement) and negative (suspected infidelity) aspects. For women, long-term health and togetherness were important goals that reinforced motivations for couples testing, whereas men often needed persuasion despite finding HIVST more flexible and less onerous than facility-based testing. Internal conflict prompted some partners to use HIVST as a way of disclosing their previously concealed HIV positive serostatus. Thus, the implementation of community-based HIVST should acknowledge and appropriately respond to decision-making processes within couples, which are shaped by gender roles and relationship dynamics.