This paper explores the perspectives of mathematics teacher leaders (MTLs) on teacher-led professional learning (TLPL). Shaped by notions of symbolic interactionism, the study employed a multisite case study design. Empirical data were collected through in-depth interviews. The study revealed the practice of TLPL influential in facilitating teacher participation and engagement in learning; encouraging long-term teacher collaboration and interaction; inviting integration of teaching experiences; inviting contextualization of professional learning; and more importantly, in promoting sustainability of professional learning of mathematics teachers. A significant implication of this study is that the education system of Tanzania needs to encourage and empower mathematics teachers to become teacher leaders for them to be able to lead and support the professional learning of mathematics teachers within their schools.