The Chinese economic reform did not launch only astonishing economic development but also gave birth to a phenomenon of overtime work. For many white-collar workers in the Chinese megacities long working hours became an inseparable part of their working life, an unwritten rule, that mostly is in contradiction with their written work contracts. Since 2006, the spread of overtime work started to be referred to as “overtime culture” (加班文化 jiābān wénhuà) and formed part of the corporate cultures of Chinese companies. The aim of this paper is to provide a complex analysis of the overtime culture as well as an answer to the research question of why the overtime culture is so widely accepted. Reasons and motivations of white-collar workers to accept the extensively long working hours include specific aspects of the Chinese culture, career development, conditions on the job market, low work effectivity, survival pressure in the Chinese megacities and the new function of the workplace as a social interaction site for young professionals.