The provision of Professional Development (PD) initiatives for English as Second Language (ESL) teachers in the university sector in Sri Lanka has become vital for teachers’ professional growth and for enhancing students’ learning outcomes. As career prospects are mostly open for graduates with higher levels of English language proficiency in Sri Lankan employment market, developing students’ English language proficiency is a key responsibility of ESL teachers in the university sector. Therefore, a broader understanding of ESL teachers’ perceptions of the need to engage in PD initiatives is essential for them to yield better outcomes from the existing PD opportunities. A qualitative case study was carried out with ten ESL teachers at Sabaragamuwa University of Sri Lanka to examine the implications of PD to prevent their career burn out and subsequently heighten their professional growth. This study employed Jean Piaget’s (1896–1980) psychological constructivism to explore the significance of PD activities to generate new knowledge in collaboration with teachers’ prior knowledge and understandings in which they may lessen their stagnation and negativity. Semi-structured interviews were used as the main research instrument and data were subjected to Thematic Analysis. Findings demonstrate that engaging in the repetitive work and responsibilities has significantly influenced teachers to become immobilised and stagnated within their employment contexts. As such, they were highly likely to develop content plateau, depression and emotional exhaustion. PD could bring new enthusiasm and stimulus into their professional practice in which they may develop potential to combat impotence, tension and burnout. Findings also conceptualised that adhering to lifelong learning via focused PD activities is a way for preventing career burn out and stagnation. However, such opportunities need to be relevant, interesting and practitioner-centred to maximise participants’ engagement and subsequent learning. Teachers also need to be aware of the repercussions of burn out and constantly examine their perspectives of teaching and develop interests to make teaching a productive profession. Although self-directed PD driven by democratic professionalism could provide potential opportunities for teachers to reduce their boredom and unstimulating work conditions, institutionally facilitated PD sessions driven by managerialism were mostly supportive to achieve this goal. Findings of the study have implications for providers and policy makers in terms of the design, delivery and framing of PD programs in ESL to harness for optimal learner outcomes through focused PD activities.