This study describes the design, development, and piloting of a universal literacy screening tool for Catalan-speaking students (Grades 1–4) within a Multi-Tiered System of Support (MTSS) framework. The instrument aims to support early identification of students at risk of reading difficulties through an evidence-based approach aligned with the school curriculum. The development followed a multi-phase process, including theoretical conceptualization, expert validation, and two pilot studies (Pil