The role of instruction in the field of interlanguage pragmatics has been regarded as having a positive effect on learners’ pragmatic development. However, most of the interventional studies conducted have only reported the immediate effects of instruction. Considering the need to examine the longterm effects of pragmatic instruction, this paper analyses the effectiveness of an inductive-deductive teaching approach to develop learners’ ability to mitigate requests, not only after immediately receiving instruction, but also four months later. Findings from learners’ responses in the three tests distributed throughout the study showed that learners employed (i) a greater amount of request mitigators, as well as (ii) a variety of internal and external modifiers, immediately after the instruction and four months later. These results indicate that the positive instructional effects were sustained over time.