A qualitative multiple case study was conducted to understand how Vietnamese high school students (n=6) experienced grammar learning by exploring their views on the role of grammar and their use of grammar learning strategies. Semi-structured individual interviews are the main instrument for data collection in this study. Using inductive content analysis, we found that all participant students acknowledged the essential role of grammar in learning English, and most of them still learned English grammar through the traditional approach. Despite the difference in the teaching approach students were exposed to, all students demonstrated a strategic approach to grammar learning, with environmental and behavioral management and cognitive strategies being the most popular strategies. The findings can help English teachers adjust their teaching approach and techniques to maximize students' grammar achievement and enhance their effective grammar learning strategies for long-term benefits. The study contributes to research on Asian EFL/ESL students' attitudes towards grammar learning and their use of grammar learning strategies.