Student engagement is paramount for the success of EFL learning. This paper explores how the leverage of a game-based learning platform, Kahoot!, into EFL grammar learning and teaching boosted student engagement. One grammar lecturer and 22 English-major students participated in this qualitative case study. Data were obtained through observations, reflective journals, and interviews. The results revealed that the platform enhanced student engagement in EFL grammar learning in six ways, namely enabling students to set goals, helping students focus more on the tasks, facilitating students to build enthusiasm and interest in learning, allowing students to experience playful learning activities, facilitating students to collaborate with their friends, and fulfilling students' need of reward and sense of competition. The students were also reported to exhibit behavioral, cognitive, and emotional dimensions of engagement during the implementation of Kahoot!. The findings have important implications for EFL grammar learning and teaching. In addition to the affordances of Kahoot!, teachers are still central to the implementation of the platform to engage the students in EFL grammar learning.