Student-teaching is the foundational professional experience for most special education teachers. We investigated the influences on preservice teachers' decision-making during their student-teaching through a two-part study. In the first phase, six undergraduate student-teachers at a large Midwestern university participated in focus group. Participants indicated that they made instructional decisions in five main areas (i.e., planning, teaching style, teaching methods, behavior management, and handling of a difficult moment) that were primarily influenced by their cooperating-teacher, previous experience, and university coursework. We then generated a survey on which 51 special education student-teachers from the same university rated the degree to which these three sources influenced the five areas of instructional decision-making. Cooperating-teachers were perceived as a significantly greater influence than university coursework in handling a difficult moment, teaching methods, and planning; and were a significantly greater influence than previous experience in behavior management and planning. Previous experience was significantly more influential than university coursework in relation to teaching style and handling a difficult moment. Implications for teacher preparation and bridging the research-to-practice gap are discussed. (Contains 4 tables.)