Using Jarvis's (2009) framework of adult learning, this study examines how inservice elementary school teachers make sense of instruction that is responsive to multilingual learners. Case studies of two teachers reveal their nuanced attempts to improve practice during a 1year, graduatelevel, addon certification program for teaching English language learners (ELLs). Findings show that different critical learning experiences afforded the two teachers opportunities to interrupt their assumptions and subsequently refine their instruction as they resolved to support ELLs. This study sheds light on teachers' ongoing sensemaking throughout a yearlong ELL endorsement program. Implications for teacher education and professional development research are discussed.