Social cognitive processes support social functioning and facilitate human social interaction. The role that the physiological condition of the body plays in social cognitive processes has been proposed by early peripheral theories of emotion. More recently, predictive coding accounts have refined this idea and suggest that bidirectional communication occurs between the brain and the body to support human social interaction. Combining multimodal techniques across experimental psychology, physiology, and neuroimaging will allow researchers to triangulate the mechanisms contributing to human social interaction, particularly by considering instances where social communication is disrupted (e.g., dementia). Interoception refers to the continual monitoring of the physiological condition of the body. Importantly, shared brain regions such as the insula, amygdala, orbitofrontal cortex, and anterior cingulate cortex are proposed to be involved in both interoception and social cognition and form part of the large-scale allostatic-interoceptive network. Disruptions in social cognition have been increasingly recognized in dementia syndromes, to varying degrees. Emerging evidence suggests that these disruptions could be linked to interoception dysfunctions due to shared neurobiological mechanisms within the allostatic-interoceptive brain network. In this review, we focused on frontotemporal dementia syndromes, Alzheimer’s disease, and Parkinson’s disease. These clinical syndromes are characterized by divergent patterns of neurodegeneration and variable degrees of impairment in interoception. Here, we review the emerging research in each dementia syndrome to date, including evidence from behavioral, electrophysiological, neuroimaging, and peripheral autonomic measures. We considered how dysfunctions in social cognition and interoception overlap in some dementia syndromes, particularly in behavioral-variant frontotemporal dementia. Finally, we propose new avenues for research to further our understanding of interoception and its involvement in dementia and other psychiatric conditions.