Concept selection is an integral stage in the design process, in which designers evaluate and compare solutions to select a smaller subset of solutions for further development. In this stage, designers often rely on their self-evaluations of solutions – either independently or using design tools – to make design decisions. However, the reliance on self-evaluations among novice designers could lead to faulty decision-making, given the presence of numerous cognitive biases. Consequently, we aim to investigate the accuracy of novice designers’ self-evaluations of the sustainability of their solutions and the moderating role of (1) trait empathy and (2) their beliefs, attitudes, and intentions towards sustainability on this accuracy. Towards this aim, we conducted an experiment with first-year engineering students comprising a sustainable design lecture and a design activity. At the end of the design activity, participants were asked to evaluate the sustainability of their own solutions and these self-evaluations were compared against expert evaluations. From the results, we see that participants demonstrate some degree of accuracy in their self-evaluations, but only with the sustainable design heuristics of longevity, sharing for maximal use, and active repair of misuse. Second, we see that trait empathy moderated the accuracy of self-evaluations, with participants reporting lower levels of fantasy and empathic concern demonstrating more accurate self-evaluations. Finally, we see that beliefs, attitudes, and intentions towards sustainability also moderated the accuracy of their self-evaluations, and participants with lower levels demonstrated greater accuracy of self-evaluations. Taken together, these findings suggest that designers’ individual differences such as trait empathy could moderate the accuracy of the evaluation of their solutions, especially in the context of sustainability.