Disagreement has been traditionally viewed as a dispreferred response, which speakers tend to avoid or mitigate due to its presumed face threatening effects. However, more recent studies argue that disagreement is not inherently dispreferred or marked, but needs to be contextualized. This article examines the interactions of Vietnamese EFL students in the context of a collaborative task in English. Somewhat surprisingly, given the common portrayal of the Vietnamese as favoring indirect communication, it finds a high incidence of direct disagreement, characterized by the use of 'no'. The study explores how direct 'no' is used in disagreement and the impact it has on the sequence of the interaction as well as the harmony of the group. In the majority of cases, and in contrast with the stated beliefs of the participants regarding disagreement, almost none of the direct uses of 'no' have negative consequences on the interaction. The analysis of instances of 'no' that impact negatively on the interaction suggests contextually interactional rules underlying its appropriate use. Group work in EFL among Vietnamese students, therefore, is another context in which disagreement is expected and does not necessarily detract from the harmony of the group.