This is a case study on the development of Mathematical Knowledge for Teaching (MKT) (Ball, Thames, & Phelps, 2008) among three pre-service teachers who are English language learners (ELLs). We investigate the potential of thinking and learning reflection logs (TLR) to promote the development of MKT. Participants were enrolled in a required course for teachers seeking middle grades certification. Data were gathered from informal interviews and participant-observation in addition to logs. Analysis focused on demonstrated use of MKT. Findings suggest that writing TLRs is beneficial for ELLs's development of MKT, among other reasons, because it necessitates the use of multisemiosis and it allows time to communicate understanding.