This paper focuses on the process by which developers regulate their moods in volatile and creative contexts. By regulate, we mean the way in which developers rationalise and act upon their moods when they encounter and interpret unforeseen challenges. Little scholarly attention has been afforded to this process, nor the concept of mood per se in IS Development (ISD). To investigate this process we conducted an in-depth field study at a computer games development organisation in Singapore. We found that plan-driven methodologies offered limited guidance when unanticipated challenges emerged, i.e. when the development process broke down due to such disruptions as staff or stakeholder turnover. Instead, developers relied on their innate faculties of mood regulation and improvisation to overcome such challenges. We offer a theory of mood-mediated improvisation, which suggests incorporating sensemaking into ISD approaches with respect to positively influencing developers’ interpretations of traumatic challenges to the ISD process.