This research investigates the impact of incorporating Inquiry-Based Research Lessons (IBRL) on teacher professional knowledge and student scientific literacy in Science 8. The study involved 85 Buenaventura Alandy National High School students, divided into two sections with similar scientific literacy levels. One section was exposed to the first implementation of research lessons, while the other experienced the second. The research process included careful planning and preparation of instruments. These instruments were validated by experts and revised as needed. Data collection involved pre-assessment tests for students and self-assessment for teachers. Employing a mixed-methods approach, the study examines the effectiveness of IBRL through qualitative classroom observations, teacher interviews, and student focus group discussions alongside quantitative pre- and post-assessment measures. Findings showed that Science teachers had high levels of professional knowledge in science content, pedagogical content, and curriculum. Implementing IBRL led to a substantial increase in the percentage of students classified as Proficient or Advanced in scientific literacy across the competencies of Explain Phenomena, Evaluate and Design, and Interpret Evidence. While there was no significant correlation between the overall effectiveness of lessons and teachers professional knowledge, correlations were found between specific aspects of teacher knowledge and lesson effectiveness. Statistical analysis indicated a significant improvement in student performance on scientific literacy post-IBRL exposure. These results highlight the value of integrating inquiry-based approaches into science education to improve teaching practices and student learning outcomes.