The development of teachers is substantial in acquiring sustainabledevelopment to achieve educational goal. The domain of teacher developmentsuch as pedagogic skills, research skills and classroom management need to beembedded in professional development program, because some factors whetherfacilitating or hindering are potential affecting their development. This studyaimed to identify the internal and external factors affecting senior high schoolEnglish Language teacher development in conducting classroom actionresearch which covered; internal factors (facilitating and hindering) and externalfactors (facilitating and hindering). This study used descriptive survey where theinstruments of collecting data covered questionnaire and interview, with 51teachers of public and private senior high schools in Jakarta. The findings of thisstudy showed that, the dominant factors that facilitated teacher developmentwere teacher colleague motivation, self and family motivation, administration andgovernment motivation. The external factors that facilitated were governmentpolicy, school facilities, sub-district and MGMP atmosphere, other duties,syllabus design requirement, the new curriculum in school, and also schoolsemester and government funding for teacher training. Moreover, hinderingfactors showed factor of school internet access and teacher paired motivation.This research concluded that, the senior high school English language teacherswere facilitated to develop their self in conducting classroom action researchthrough internal and external factors.