This study examined the level of understanding of sustainable development principles among students at the University of Wasit (Iraq), investigating statistically significant differences between scientific and humanistic specialization students, as well as by gender. A descriptive-comparative methodology was adopted. The sample comprised 200 male and female students distributed equally across four colleges: the Colleges of Science and Engineering (scientific track) and the Colleges of Arts and Education (humanistic track), with 50 students per college. The Sustainable Development Understanding Scale developed by Michalos et al. [1] and re-validated by Leal Filho et al. [2] was applied across four dimensions: general knowledge, environmental, economic, and social. Results revealed a moderate overall understanding level (M = 3.09 out of 5), with science students significantly outperforming humanities students in the environmental dimension (M = 3.71 vs. M = 2.86, t = 7.94, p < .001), while humanities students showed deeper understanding in the economic and social dimensions. A behavioural gap was equally evident in both groups, suggesting that disciplinary knowledge alone does not bridge the knowledge–behaviour divide. The study recommends integrating sustainable development courses as compulsory requirements across all University of Wasit specializations, alongside a cross-disciplinary institutional strategy.