The purpose of this quasi-experimental study was to examine the effect of music mnemonic and flash cards in enhancing grade 4 students' English vocabulary acquisition. The participants were 30 students, aged 9-11 years old, who had low capability in second language (English) vocabulary acquisition. The result of the study showed that music mnemonic and flash cards could increase students' vocabulary acquisition, p = 0.001; p < 0.01. Music mnemonic group has the highest score due to the multimodality of the various methods of memorization that impact to the chunking effect on working memory, so that the new information can be more easily to transfer to the long-term memory. Teachers and school should combine several methods in providing appropriate learning based on the students' cognitive development stage.