Mental imagery is what we experience when we imagine seeing a specific object, hearing a particular sound, or feeling a particular touch, and it is perhaps the most fundamental aspect of our imagination. Historically, research on mental imagery has explored the phenomenological and neurological similarities between mental imagery and sensory perception to understand the quasi-perceptual nature of these conjured “images” we experience in the “mind’s eye.” However, this line of research has traditionally focused on the similarities of mental imagery and perception within each sensory modality, and the relationship between mental imagery in one sense and its effects on perception in another sense or on our perception of the world around us as a whole has largely been ignored. This chapter will extend the study of the relationship between mental imagery and perception into a multisensory context, and utilize insights from research in neuroscience and multisensory perception to explore how mental imagery in one sense can affect ongoing perception in another. The chapter will also examine the similarities in how the brain processes and integrates imagined and real crossmodal sensory stimuli. Lastly, the chapter will discuss how the integration of mental imagery and real sensory stimuli can lead to brain plasticity across the senses and change how we perceive the world around us in the future.