Design decision-making in infrastructure tenders is a challenging task for contractors due to limited time and resources. Multi-criteria decision analysis (MCDA) promises to support contractors in dealing with this challenge. However, the ability of MCDA to ensure decision quality in the specific context of infrastructure tenders has gained little attention. By undertaking a longitudinal case study on early design decisions in a tender for a design-build project in the Netherlands the relationship between MCDA and decision quality is investigated. The case results show that in the early tender phase the decision making very much relies on the experience and knowledge of engineers. If MCDA is inappropriately used in such a context it can create impressions of soundly underpinned evaluations of design options while neglecting uncertainties and leading to low-quality decision. Although MCDA defines the “what” is required for structuring the decision problem, it does not support decision-makers in the “how” to do it. The explicit consideration of decision quality elements in MCDA can support the “how” and can create awareness for decision makers concerning importance, scope and uncertainty of criteria.