The article demonstrates an action research approach for constructing Transformative Sustainability Pedagogy (TSP) to empower teachers for a sustainable future. The starting point for the TSP was a Transformative Education for Gross National Happiness (GNH) teacher action research project in Bhutan (2010-2013) -- a collaboration between the author, co-researcher and the Royal Education Council. Two Leadership Training Courses (LTC) were developed for teachers from seven schools based on critical/transformative pedagogy. The aim of the courses was to empower the teachers to carry out action research to infuse their schools with GNH principles and practices. The project concluded in 2013, and the results showed that the LTC transformative pedagogy and action research approach had successfully empowered teachers to act and promote GNH in their schools. Nine years on, the author re-analyzed the project data to identify the empowering pedagogical principles and construct TSP grounded in ecological principles and values.