Purpose: The purpose of this paper is to present the results of a classroom assessment aimed at determining the extent to which five key sustainability competencies develop in students during an introductory transdisciplinary sustainability course. University sustainability programs intend to provide integrated education that fosters the key competencies students need to solve real-world sustainability problems. Translating sustainability competencies into effective pedagogical practice in integrated academic programs is not straightforward. This work builds on a previous study by both expanding the competencies evaluated and considering additional demographic characteristics. Design/methodology/approach: The paper summarizes previously identified key sustainability competencies and describes teaching methodologies used to foster these competencies in students. Development of competencies in students during a semester-long course is assessed using a pre-/post-test based on two case studies. The implications of the findings for teaching practice and overall program structure are discussed. Findings: Based on the assessment methods used here, four of the five sustainability competencies evaluated in this study developed differently in students according to gender, disciplinary affiliation and age. Females improved interpersonal competence more than males. Systems thinking competence improved for students associated with the three disciplinary affiliations considered in this study: sustainability major, sustainability minor and business major. Anticipatory competence improved for sustainability and business majors only, but not for students minoring in sustainability and majoring in other disciplines. Finally, normative competence improved for younger students only. Research limitations/implications: Insights for teaching practice and overall program structure are based on assessment of one introductory transdisciplinary sustainability course. Much additional work is needed to draw strong conclusions about general teaching practices and program structure for sustainability education. This study provides a flexible and field-tested rubric for further evaluative work in other sustainability courses or degree programs. Practical implications: Universities incorporate sustainability into their undergraduate curricula in many ways, ranging from certificates to entire degree programs focused on sustainability. The results of this study suggest that educators pay attention to gender diversity, classroom teaching practices, disciplinary perspectives and student attitudes and developmental stages as they figure out how to make sustainability part of undergraduate education. This information may help create more effective sustainability courses and academic programs, which may maintain the viability of current sustainability programs and promote the institutionalization of sustainability in higher education. Originality/value: This research contributes to undergraduate sustainability education by providing insight into how sustainability education might thoughtfully be integrated into academic programs. It also offers an assessment approach for use by other sustainability educators to evaluate effectiveness of teaching practice and overall program structure based on five key sustainability competencies commonly cited in the literature.