This study assessed Developmentally-Appropriate Practices (DAP) among Mercedes District teachers for teaching early numeracy to grade one learner, focusing on the development and evaluation of DAP-based supplemental learning materials. Using a descriptive-developmental evaluative method, 248 grade one learner, 45 teachers, and 5 Master Teachers, an Education Program Supervisor, and Division LRMS coordinator participated. Findings revealed a frustration level in early numeracy skills before exposure to DAP interventions, with common least mastered competencies including visualization of numbers and understanding inverse functions. Teachers demonstrated developmentally-appropriate practices, employing pedagogies connecting early numeracy to real-life scenarios, utilizing visual aids, facilitating manipulative-based activities, and emphasizing manipulative-based assessments. The study produced DAP-based materials aligned with curriculum competencies, adhering to DepED standards, significantly enhancing learners post-intervention performance. A notable improvement in early numeracy skills affirmed the effectiveness of DAP-based materials. Recommendations included developing digital versions, involving parents, and proposing separate DAP-based materials for each identified least mastered competency in early numeracy.