Tipping behavior continues to intrigue economists, psychologists, and hospitality management researchers primarily because tipping is a voluntary payment that does not buy something real in return. Yet, it is still a major source of income for millions of workers. This chapter offers a glimpse into the main reasons why people tip. Since consumers’ psychological and social motivations can better account for tipping behavior than economic considerations, the following sections present key studies on the behavioral factors that affect tips. Future directions are discussed.