This study heeds a decade-long call to action to examine the accessibility of Schoolwide Positive Behavioral Interventions and Supports (SWPBIS) for students with severe disabilities. To improve the accessibility of SWPBIS, Universal Design for Learning (UDL) and evidence-based practices were used to teach three students with severe disabilities schoolwide behavior expectations in inclusive schoolwide settings. Special education teachers from three different elementary schools adapted their campus SWPBIS Tier 1 lesson plans with additional visual supports, social narratives, and systematic instructional procedures. All participants showed improvement as evidenced by a reduction in the duration of their problem behavior in schoolwide settings. Implementing teachers found the intervention and corresponding materials to be socially valid.