This paper presents a study of the development of L2 pragmatic competence in the speech act of criticisms. Data were collected from three proficiency groups of Vietnamese foreign language learners of English via a conversation elicitation task and a written questionnaire. An interview was also conducted to probe into the learners’ pragmatic decision-making. Results show that the strongest difference among the learners lay in the area of modifiers to criticisms, rather than in the criticism strategies per se. Specifically, as the learners became more proficient in the L2, they mitigated their criticisms more often, thanks to a better control over language processing. However, they still lagged far behind the native speaker group in the frequency of their use of mitigators. These proficiency effects were explained by the EFL context, which probably did not much facilitate pragmatic development, given the learners’ insufficient exposure to the target norms.