This study aimed to determine the effectiveness of the "Thirty Days of Joyful Reading" program in improving the reading proficiency of Grade 10 students at Pacita Complex National High School in San Pedro City. A significant number of students showed low reading levels based on the Philippine Informal Reading Inventory (Phil-IRI) Pre-Test, with an average score of 13.8. This indicates a major educational challenge, further emphasized by the Philippine Statistics Authority's statement that millions of students graduate with poor reading skills. The “Thirty Days of Joyful Reading” program is an intervention developed to address this problem. It used reading materials specially created for the students, designed to be interesting and appropriate for their level. The program's effectiveness was assessed using a mixed-methods approach, including the Phil-IRI Pre-Test and Post-Test, and a four-part survey questionnaire. The questionnaire included demographic questions, statements about the effectiveness of the materials and the overall program (using a 4-point Likert scale), and an open section for student comments and suggestions. The data were analyzed using Jamovi for quantitative data and MaxQDA for thematic analysis of qualitative data. The results showed a significant increase in the average Phil-IRI Post-Test score, from 13.8 to 40.3, reflecting a 26.5-point improvement. Students also demonstrated high satisfaction levels with the materials and the program, confirming the effectiveness of the "Thirty Days of Joyful Reading" program in improving students’ reading proficiency.