This study explored the integration of technical vocabulary into pre-observation conferences and its influence on English teachers' professional learning and discussion in their post-observation conferences. The conceptual framework based on Harvey [2011. "A Sociocultural-Theory-Based Study of the Impact of Mediation During Post-observation Conferences on Language Teacher Learning." Unpublished doctoral diss., University of South Florida] and Goe, Biggers, and Croft [2012. "Linking Teacher Evaluation to Professional Development: Focusing on Improving Teaching and Learning." Denver, CO: National Comprehensive Center for Teacher Quality] was used to analyse the questionnaire, audio recordings, and documents collected in seven peer observations of teaching in Taiwan. This study has two major findings. First, English teachers regarded the technical vocabulary as stimuli for their professional learning; however, the range of technical vocabulary used during the post-observation conferences was limited. Second, three major factors affected their use of technical vocabulary. A new model was proposed in order to effectively integrate technical vocabulary into peer observations of teaching for elementary school English teachers' professional learning.