The objectives of the study were to introduce the technique called "Mnemonic Keyword Method" ("MKM") to low proficiency English learners, and to explore the effectiveness of the method in terms of short-term and long-term retention. The sample was purposefully drawn from one intact class consisting of 44 students. They were first-year university students studying a non-credit English remedial course. The materials used in the study consisted of 40 target words, with half of them taught using MKM and the other half with mixed methods, namely contextual clues, word structure analysis, and opposite word-pairs. Students' retention was measured by using a 40-item-vocabulary test and two cued-recall sheets. The results from the vocabulary test and the cued-recall sheets showed that compared to those mixed methods, words taught by MKM could be better recalled both in short-term and long-term memory.