The five chapters of this dissertation are anchored around the theme of supporting teachers in making inclusive instructional decisions in science to facilitate active student participation and engagement in science learning for students with complex support needs (CSN). Chapter 1 describes the benefits of inclusive education for students with CSN. In addition, the benefits for students with CSN learning next-generation, multidimensional science expectations (NGSS Lead States, 2013) are discussed. Chapter 2 includes a scoping review to understand more about the characteristics of multidimensional science instruction for students with CSN. This review expands on previous reviews to examine the types of science learning objectives included in the studies, the cognitive demand of the learning objectives, and whether the instructional approaches used facilitate understanding of the objectives. The following chapter, Chapter 3, describes the design and development process of a tool supporting inclusive science decision-making for teachers of students with CSN. The Inclusive Science Decision-Making Tool (ISD-MT) is informed by Ruppar et al.'s (2022) framework for educational decision-making while foregrounding science learning. The tool includes four components: what to teach, how to teach, value-based decisions, and reflections after teaching. The ISD-MT includes four learning activities and is designed for flexible implementation into larger science lessons and units in inclusive science classrooms. Chapter 4 describes a study to validate an approach to inclusive decision-making reflected in the ISD-MT and examine the perceived acceptability of the approach and feasibility of the ISD-MT to implement the approach. Focus groups and interviews were conducted with special education teachers, and findings revealed that teachers found the approach to decision-making and the science learning activities within the ISD-MT were acceptable. Chapter 5 provides a discussion of the overall findings from the previous chapters and recommendations for future research. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]