In applied linguistics, the scope of emotion research has broadened from the simple linear cause and effect paradigm of anxiety to multiple facets of emotions and their interaction with various aspects of language learning. Along with this development, the social dimension of emotions is currently receiving an increasing amount of research attention. The present study has continued that focus by exploring the trajectories of changing emotions throughout the lifelong experience of English language learning and language use among Vietnamese EAL tertiary teachers and EAL teacher candidates in a single Vietnamese university. The study also highlights the role of emotion in their English oral communication. This study employed a qualitatively-driven mixed methods research design. Two phases of data collection using initial and exploratory self-designed questionnaires, followed by semi-structured interviews and reflective journals took place over approximately six months. The quantitative data, collected from all EAL teachers and their final-year students in the English faculty, aimed to capture the range of emotions the participants experienced in speaking English. The qualitative data, collected from nine teachers and ten students recruited from the questionnaire phase, revealed the complexity and dynamism of their emotions in the process of language learning and use. It also sought to understand the rich sources of their emotions, and the influences of emotions on their oral communication. LimeSurvey was employed to collect and analyze the questionnaire data, and thematic analysis was used to analyze the qualitative data. The findings show that the participants experienced shifting emotions across the different contexts of language learning, including family, school, out-of-school, tertiary and professional contexts. The emotions were seen to be dynamic, socially and contextually constructed, emerging from their social circumstances and interaction with others. They were interwoven with self-concept, language learning success, perceived standing in different communities, and relationships with others. Emotions also appeared to play a significant role in motivating the participants to take up English for their teaching profession. Theories of belonging, agency and positioning, as well as L1 cultural values informed the interpretation of the data to help explain the complexity of emotion for these participants. The results also provide theoretical and practical implications for emotion research and pedagogies of EAL teaching and learning. The participants’ emotional self-regulation was not dealt with in this study because there was little evidence in the data.