Animals have accompanied humans for thousands of years, with a strong bond forged between humans and other species. Our relationships with animals can take different forms. On one hand, animals can serve instrumental purposes: We currently use animals for clothing, for testing a range of human products, for gaining basic insights into human biology and behavior, and as food. On the other hand, human–animal relations are social. The clearest example is the practice of pet keeping, with people attributing a special status to their companion animals. We review the current state of research on human–animal relations by focusing particularly on companion animals and on the psychological mechanisms involved in this special relationship. Our aim is to highlight key findings from human–animal relations research that also have implications for different scientific disciplines.