Teachers of English as a Second or Other Language (TESOL) have a tradition of active participation in professional development activities. Despite the growing importance of formal and informal workplace learning transforming the notion of professional development, most institutions persist in rigid and prescriptive ideas of what consists appropriate learning for the workplace. The aim of this research was to determine the types of meaningful learning activities for TESOL teachers and their defining characteristics. The theoretical framework of social learning and particularly, Communities of Practice, was used for this research. A mixed methods approach was used with an anonymous online questionnaire and semi-structured interviews which provided richer, more descriptive data. The findings showed that TESOL teachers’ primary concern is mastery of their practice and that they undertake a wide variety of learning activities for the workplace beyond the narrow professional development scope usually intended for their subject area. The wide range of learning trajectories TESOL teachers follow in their career reflects the variety of their global teaching contexts and their own career ambitions. The research found that, in addition to formal professional learning, most of the new information, skills and practices TESOL teachers need in their careers are acquired through social interactions and continuous informal learning taking place at the workplace. Formal professional development plans need to incorporate and acknowledge this type of workplace learning.