Background: Low student learning outcomes are often associated with low reading interest. Reading interest plays an important role in improving students’ understanding, knowledge, and academic achievement. Therefore, increasing students’ reading interest has become an important concern for teachers and schools. Objective: This study aimed to determine the effect of reading interest on students’ learning outcomes and to identify its contribution to learning achievement. Method: The study employed a correlational associative research design. The research was conducted at SMA Plus Merdeka Soreang during the 2024 academic year. The sample consisted of 38 second-grade students selected using a population sampling technique. Data were collected using reading interest and learning outcomes questionnaires and analysed using Pearson correlation analysis and simple linear regression. Result: The findings revealed a significant positive relationship between reading interest and students’ learning outcomes, with a correlation coefficient of 0.747 and a significance value of 0.000. Conclusion: The study concludes that reading interest strongly influences students’ learning outcomes. Originality/Value: This study offers empirical and practical novelty to secondary educational evaluation by demonstrating the strong predictive association and significant contribution of reading interest toward academic achievement and conceptual comprehension across subjects within a private high school setting, an area that remains limited in direct correlational documentation. These findings enrich the empirical literature and serve as a strategic reference for educators and institutional policymakers in designing school-wide literacy initiatives and habit-forming reading interventions to elevate student learning outcomes systematically.