The object of this grounded theory study was a three year long, public sector inter-organizational information system (IOIS) project which spanned four user organizations, two suppliers, one national organization, a research organization and a Government Ministry. The data were elicited by means of narrative stories, observations of project meetings, diaries, project memoranda and emails sent by project members to each other during these years. Glaserian grounded theory method was used as the technique for theory building. Three core categories were identified: governance, power and emotions. The study offers two key contributions: first, it builds a substantive theory of Emotions of Control in an IOIS project, presented in the form of propositions. The theory offers an approach to understanding the meaning of emotions in project work and the consequences of emotions in collaboration. Second, we offer a window into the theory building process using Glaserian grounded theory. We argue that the findings of this study have some implications of value to researchers studying emotional issues in IOIS projects or information system (IS) projects in general, because the role of emotions in project work can be pivotal in determining project success.