Recent research in cognitive linguistics has shown that idiomatic phrases are decomposable and analyzable and that the individual words in idiomatic phrases systematically contribute to the overall figurative interpretations. This cognitive linguistic view suggests that enhancing awareness of conceptual metaphors embedded in the individual words may help second language students to learn idioms. This study examined whether enhancing awareness of orientational metaphors of particles facilitates acquisition of phrasal verbs by Japanese English as a foreign language (EFL) students. The students in the control group learned a set of phrasal verbs through traditional instruction, whereas those in the experimental group received the same input through a cognitive linguistic approach. The students in both groups were then asked to fill in the missing adverbial particles of the phrasal verbs. Results showed that the students in the experimental group performed significantly better than those in the control group, implying that when the target idioms are not stored as a unit in learners' mental lexicon, learners who are aware of conceptual metaphors may rely on metaphorical thought to produce an appropriate adverbial particle. This highlights the implications that EFL learners need to be explicitly taught about the notion of orientational metaphors before they can actively comprehend and produce appropriate phrasal verbs. (Contains 5 tables and 2 figures.)