Modality switching cost indicates that people's performance becomes worse when they judge sequential information that is related to different sensory modalities than judging information that is related to the same modality. In this study, we conducted three experiments on proficient and non-proficient bilingual individuals to investigate the modality switching costs in L1 and L2 processing separately. In Experiment 1, materials were L1 and L2 words that were either conceptually related to a visual modality (e.g., light) or related to an auditory modality (e.g., song). The modality switching costs were investigated in a lexical decision task in both L1 and L2. Experiment 2 further explored the modality switching costs while weakening the activation level of the perceptual modality by adding a set of fillers. Experiment 3 used a word-naming task to explore the modality switching effect in language production in L1 and L2. Results of these experiments showed that the modality switching costs appeared in both language comprehension and production in L1 and L2 conditions. The magnitude of the modality switching costs was conditionally modulated by the L2 proficiency level, such as in the L2 condition in Experiment 1 and in both L1 and L2 conditions in Experiment 3. These results suggest that sensorimotor simulation is involved in not only language comprehension but also language production. The sensorimotor simulation that is acquired in L1 can be transferred to L2.