Although English learners (ELs) are one of the fastest growing groups of students in the United States, many teacher preparation programs have yet to require preservice teachers (PSTs) to receive training in effective practices for teaching ELs. We examined four elementary PSTs’ instructional practices when implementing cognitively demanding mathematics tasks with ELs during a 4-week field experience. Through interviews, observations, and written reflections, we found that the PSTs tried to support the ELs, with varying degrees of success, by allowing for multiple modes of communication, including visual supports, pressing for explanations, and checking for understanding. The PSTs’ use of these strategies during the field experience was largely in response to the ELs’ use of language rather than mathematics. Furthermore, although the PSTs’ attention to linguistic supports was well intentioned, it often resulted in the PSTs taking on much of the mathematical thinking or failing to consider different student mathematical conceptions. We conclude that explicit instruction in and reflection on effective instructional strategies with ELs, set in authentic experiences, could help PSTs to more effectively develop the knowledge and skills necessary to meet the needs of ELs in the mathematics classroom.