Social security is one of the key pillars of socioeconomic development in developing countries. Despite being an internationally recognized basic right and a key pillar of socioeconomic development, it does not protect the majority of the global workforce. Over 90% of workers in developing countries do not have social security coverage, the greatest percentage belonging to informal sector. In Rwanda, the national government has stepped up efforts to extend coverage to the wider population, but informal sector workers have not joined the existing pension scheme in significant numbers, and the reasons for which are unclear. Guided by Maloney's theory of voluntarism; the purpose of this phenomenological study was to examine the factors affecting the level of workers' participation in informal sector in pension scheme in Rwanda. This study was designed to provide new insights into the current social security situation of informal sector workers in Rwanda and to contribute to the knowledge base on social security and the informal sector. The research questions focused on awareness, income levels, and other factors that can address the social security needs of informal sector workers. Data were collected from 22 active workers from informal sector and 5 officials from ministries and agencies who were well-versed with social security issues. Data were analyzed via Moustakas's steps of epoche, phenomenological reduction, imaginative narration, and synthesis of texture and structure. The results revealed that low incomes, lack of awareness, poor benefit design, distrust of public schemes, and frustrating laws and procedures were hindering the increased public pension coverage of informal sector workers in Rwanda. These findings will help Rwandan policy makers to promote positive social change by informing policies that enhance social protection of workers in informal sector.