The study, “Students Breadth and Depth of Vocabulary Knowledge in Relation to Writing Proficiency: Basis for an Enhancement Program,” examined the relationship between vocabulary knowledge and writing proficiency among Grade 11 students at PHINMA Araullo University. Specifically, it explored how vocabulary breadth and depth are associated with the students writing ability with organization, coherence, cohesion, and mechanics. The study also investigated how the student profile variables, sex, strand, academic performance, and favorite subject, relate to vocabulary performance and writing skills. A descriptive-correlational design was employed, involving 228 Senior High School students enrolled in the Reading and Writing Skills subject during the second semester of the school year 2024–2025. The data were collected using standardized vocabulary assessments and a writing proficiency rubric. The results showed that the students had moderate vocabulary breadth and depth levels. The writing proficiency was rated excellent in organization and proficient in coherence, cohesion, and mechanics. Significant positive correlations were found between vocabulary breadth and depth and writing proficiency. The academic strand, general average, and favorite subject were also significantly associated with vocabulary and writing scores, while sex had no statistically significant influence. Based on these findings, the WriteVocab Plus Enhancement Program was developed. The program includes eight integrated components: Word Vault Journaling, Contextual Essay Writing, Read-Reflect-Respond, Peer Writing Clinics, Lexis Game Hour, E-Portfolio Compilation, Language Ladder Challenges, and Vocabulary Episodes Vodcast. These components are designed to align with PHINMA Araullo Universitys blended learning modality and aim to strengthen vocabulary acquisition and writing performance through consistent, engaging, and reflective practices. The study recommends the implementation of the WriteVocab Plus Program in the Reading and Writing classes and the regular monitoring of student progress. It also suggests adapting and testing the program across other strands and school contexts to validate its broader applicability. The findings highlight the importance of integrating vocabulary instruction into writing tasks to promote student success in academic literacy.