This paper considers the effects of perceptual and mental imagery on the rate of retention of meaning and form of L2 idioms. A group of 34 pre-intermediate Japanese students of English learned 30 target idioms. For 15 idioms etymological notes were provided, whilst the learners themselves illustrated the remaining 15 idioms. Both approaches stimulated imagery processing. Etymological notes were found to promote the retention of idiom meaning whilst pictorial support enhanced the recall of their linguistic form. This paper examines the possible reasons behind the findings and their pedagogical implications.