Abstract This case study explores an English learner (EL) teacherâs lived experiences of emotions concerning teacher collaboration in the US. The analysis of the EL teacherâs weekly journals and the recordings of her bi-weekly meetings with a teacher educator demonstrates that the teacher experienced a great amount of emotion labor under the feeling rule of âbeing supportive.â The major sources of her emotion labor include (1) content teachersâ lack of training concerning ELs; (2) the lack of systematic administrative support; and (3) her perceived teacher identity. The analysis also shows how her emotional reflexivity developed through reflection and collaborative dialogue with her mentor on her emotional experiences, empowering her to take a more active role in building a professional partnership with content teachers. The article ends with implications for language teacher education and further studies on language teacher emotions.