A series of worldwide projects concerning assessment, student outcomes and quality in higher education has revealed the need for a change in how higher education institutions assess student outcomes; however, many academics remain unconvinced. The success of assessment change arguably depends on the assessment culture within the institution. This qualitative investigation of assessment cultures draws on the perspectives of 35 academics from Australia, Canada and Sweden. Data were analysed through a socio-cultural lens, with results supporting assessment cultures related to institutional structures and collegial relationships. The results also suggest the existence of assessment microcultures embedded in disciplines. This study provides concurrent validity to previous studies of assessment cultures, evidenced from institutional leadership perspectives, through the analysis of academic practitioners' viewpoints. Synthesis of findings observed that a combination of agency for change and policy levers effectively stimulated change. Included are suggestions to address the perceived barriers of entrenched disciplinary practices, institutional systems and logistical constraints. There is limited empirical research on the impact of assessment culture on assessment practices; this study addresses this shortcoming and provides a new aspect to add to the literature on assessment cultures in higher education.