This study explores the role of motivation in second language acquisition (SLA), emphasizing how different types of motivation influence learners’ engagement, strategies, and proficiency. Drawing on the theoretical frameworks of Gardner and Lambert’s integrative and instrumental motivation and Dörnyei’s L2 motivational self-system, the research employs a mixed-methods approach with 60 intermediate-level English learners. Quantitative analysis of motivation questionnaires and qualitative analysis of semi-structured interviews reveal that integrative and intrinsic motivation are strongly associated with higher language achievement, while instrumental motivation supports sustained effort in structured contexts. The findings highlight the dynamic nature of motivation and underscore the importance of fostering both internal and social motivational factors in language learning environments. Recommendations for educators focus on goal-setting, authentic language practice, and creating culturally relevant learning experiences.