Designers’ empathy plays an important role in supporting socially conscious design. Although widely studied in engineering design, a majority of the research on empathy focuses on designers’ ability to empathize with primary users; little attention is given to empathizing with those affected in a secondary or tertiary capacity—an important consideration when evaluating the broader impacts of design decisions in the context of environmental sustainability. Moreover, little research has investigated the influence of designers’ internal traits (e.g., beliefs, attitudes, and intentions) on their emphasis on environmental sustainability. Such an investigation could reveal the role of developing internal and interpersonal traits in sustainable design education. In this paper, we explore this gap by introducing student designers to a hands-on sustainable design workshop. We compared changes in their trait empathy and their beliefs, attitudes, and intentions toward sustainability from before to after the workshop. We also compared the relationship between these individual differences and participants’ self-evaluated sustainability of their solutions. We see that participants reported an increase in their beliefs and intentions toward sustainability and a decrease in personal distress from before to after the workshop. Furthermore, participants who received the sustainable design lecture reported that their solutions were more sustainable in terms of disposal, salvaging, and recycling. Finally, trait empathy significantly predicted the self-evaluated sustainability of solutions on the following dimensions of sustainable design: disposal, recycling, and finding wholesome alternatives. These findings call for future work into the influence of designers’ individual differences on their approach to sustainable design.