PurposeBy using the lens of effectuation and causation, this paper aims at exploring how the team is formed in high-tech academic spinoffs, by looking specifically at decisional heuristics in an academic context. Indeed, the team composition is a critical issue for the subsequent growth of the academic new venture: on the one hand, the scientific-centred knowledge of the academic entrepreneurs is one of the main elements that lay the foundation for the new venture; on the other hand, it has been widely recognized that the lack of market-related knowledge and experience often has detrimental effects on performance. Decisive is then to explore how team decisions pertaining to the team formation process are taken.Design/methodology/approachA qualitative methodology based on multiple case studies is adopted under an abductive approach.FindingsResults shed light on how decisions pertaining to team formation are taken by academic entrepreneurs and with what effects on team composition, a fundamental element to foster the growth of academic new ventures. Specifically, this study derives some propositions about the adoption of effectuation and causation in the team formation process, their occurrence and sequence in the light of the scientific context in which academic new ventures spin out and the effects on the team composition.Originality/valueThis study contributes to the debate on academic entrepreneurs’ decisional heuristic and the use of effectuation or causation in the early stages of an academic new venture, by focusing on the team formation process. This study specifically considers three temporal micro-phases – the selection of founders before inception, the appointment of top management teams, and the integration of early employees after the inception – and whether the academic context influences the decisional heuristics. Managerial implications are also derived.