Abstract: Complexity in megaprojects leads to uncertainty about the future, which means forecasting is difficult, and perceptions of uncertainty can differ among stakeholders based on differing interests and values. We contribute to uncertainty and stakeholder management research and practice in megaprojects by conceptualising perception of uncertainty and by adopting Q methodology as a mixed method for stakeholder analysis to empirically study stakeholders’ perceptions of uncertainty in the Flemish A102 road project. Four perception groups are revealed that show why understanding perceptions of uncertainties in megaprojects matters: (i) uncertainty management must be broadened by considering relations between uncertainties; (ii) assessing whether uncertainties are irreducible or reducible and how they should be managed can be perceived differently; (iii) stakeholder analysis must aim to understand stakeholder heterogeneity and avoid classifying stakeholders based on a priori assumptions; (iv) revealing perceptions of uncertainty can help project managers anticipate conflict and prepare for stakeholder dialogue and engagement.