This study addresses the need to reinforce the reading learning of students with intellectual and developmental disabilities (IDD) in general education classrooms. A standardized way of assessing support needs in reading (SNr) from the teachers’ perspective is proposed. The objectives were (i) to develop an instrument and evaluate its properties and (ii) to preliminarily assess the support needs in reading of students with IDD. Participants were 86 Chilean elementary school teachers who responded about the support needs of their own students. The instrument assesses three dimensions (i.e., representation, engagement, and action and expression). Analyses showed excellent preliminary evidence of validity and reliability. Preliminarily identified support needs suggest that students need more support in representation. Practical and research implications are discussed.