Hackathons have attracted increasing interest in recent years, and whereas much of the research focus on the role of hackathons as potential means for education, innovation, or municipal engagement, this paper focuses on the creative process of a hackathon. We present an explorative, autobiographical case study of a team at a hackathon and in the analysis we identify four factors, which in particular impacted the team’s design judgement during the hackathon: 1) The hackathon format, 2) the available tools and materials, 3) the participants’ domain knowledge, and 4) the participants’ technical knowledge. Though the factors are evident in most design processes, we discuss how the four factors in a hackathon setting influenced the design judgement in a particular way and how the factors influenced the creative engagement in developing technology in the hackathon. We discuss potential implications for future research on how to understand design judgements made under the particular circumstances of a hackathon.