Under the lens of a sociocultural view, this qualitative study was conducted with 83 non-English major learners at a university in the Mekong Delta to examine English learners’ task engagement. Twelve of them were further invited to be interviewed. Data were collected from class observations, learning journals, semi-structured interviews and stimulated recall. The study showed that the same task was performed differently by learners, and that the way learners implemented a given task was shaped by the negotiation between their personal and contextual factors because of their sense of agency in the situated sociocultural learning context. The study has acquired an increased insight into learners’ task engagement regarding their agency in the teaching and learning context of Vietnam from a sociocultural view.