The term "grammar learning strategies" refers to the various approaches or techniques that learners use to acquire and internalize grammatical rules and structures of a language. This master’s thesis investigates the relationship between grammar learning strategies and learners' achievement in the context of two grammar schools located in Osijek and Slavonski Brod. The study employs a quantitative research approach, utilizing a questionnaire administered to learners in both schools. Data from the questionnaire is analyzed using the SPSS statistical software. The research explores the concept of grammar learning strategies, focusing on how different learners employ specific techniques and approaches to acquire grammar knowledge. Furthermore, the study examines potential differences in strategy use and achievement between male and female participants, as well as among participants from lower and upper classes. The findings shed light on the effectiveness of different strategies in grammar learning and provide insights into how achievement, gender, and other factors may influence language learning outcomes. The results contribute to the existing literature on language acquisition and offer practical implications for educators and curriculum designers to enhance grammar instruction in school settings. By better understanding the relationship between grammar learning strategies and learners' achievement, this research seeks to improve language learning outcomes for students in Croatian schools.