This study delves into understanding the determinants of grit in English learning among Vietnamese students, highlighting both external and internal factors. Utilizing qualitative interviews, the research engaged with a cohort of 15 students, aiming to unearth the intricate interplay of influences that bolster their commitment and persistence in English studies. External factors emerged prominently, with teacher influence playing a significant role. Teachers’ motivational techniques, personalized feedback, and the establishment of a nurturing learning environment were underscored as pivotal in shaping students’ determination. On the internal facet, personal goals and aspirations, self-efficacy, intrinsic curiosity for the language, adaptive learning strategies, peer comparisons, and reflective self-assessment were identified as central elements. Insights from Constructivism and Socio-Cultural Theory were instrumental in interpreting the findings, revealing how individual experiences intersect with broader societal and cultural narratives. The study uncovered that while personal motivations and aspirations drive the students, they are simultaneously influenced by societal values, especially in the Vietnamese context, where education is deeply revered. This research contributes to the growing body of knowledge on grit in educational settings, shedding light on the unique cultural and individual determinants in the context of Vietnamese students learning English.