PurposeThe theories of transaction‐cost economics, the resource‐based view and the core competencies approach have been used extensively to justify the rationale behind strategic decisions on outsourcing, but their validity has not been investigated yet in comparative empirical research. Additionally, no study has examined the operational effects of these decisions in‐depth. The purpose of this paper is to fill these two gaps in the academic literature.Design/methodology/approachA literature review confirms the existence of these gaps and informs hypotheses based on the three theories. Additionally, the model for continuous decision making on outsourcing is used to systematically collect data from five cases studies. The cases – all make‐to‐order or engineering‐to‐order – have been analysed on effects for operational performance and control resulting from strategic decision making on outsourcing.FindingsFrom this evaluation, it appears that these companies perform weakly on the control of the outsourced activities. Furthermore, it seems that the (manufacturing) strategy is disconnected from outsourcing practices and that outsourcing hardly contributes to competitive advantage. Moreover, from some of the case studies it appears that the decision for strategic outsourcing is irreversible. Finally, traditional criteria and behaviour during decision making prevail, i.e. a cost‐driven perspective, which does not address contemporary challenges.Research limitations/implicationsDespite being explorative and based on only five cases, these findings indicate that strategic decision making on outsourcing based on the three theories insufficiently accounts for operational issues that emerge later during manufacturing; it might be necessary to revise the theoretical base for outsourcing to include management of outsourced manufacturing activities.Practical implicationsThe findings imply also that managers in companies, in any case those firms that operate on the basis of make‐to‐order or engineering‐to‐order, should be less “rushed” into strategic decision making on outsourcing that has adverse effects. Rather, outsourcing requires integral decision making in contrast to factual decision making that displayed signs of bounded rationality (particularly expressed through the focus on cost savings).Social implicationsThe dominant, one‐sided view of the cost perspectives contributes to the notion that the shareholders' interests for short‐term profitability conflict with long‐term organisational health (apparent through the impact on operational management of outsourcing activities).Originality/valueStakeholders involved in strategic decision making might use this research to evaluate fundamentally decisions that cover outsourcing. At the same time, for consultants and practitioners it offers insight that is complementary to the often one‐sided strategic decision making with its focus on cost reductions. Furthermore, this paper demonstrates the limited validity of current theories that underpin strategic decision making on outsourcing and provides an impetus for academics to develop more appropriate theory.