PurposeThe purpose was to present a developed, tested and evaluated methodology for assessing teamwork and sustainable quality culture, focusing on top management teams (TMTs).Design/methodology/approachThe developed methodology was based on a convergent mixed-method design, including two data collection methods: questionnaire and focus group discussion. Two pilot tests were performed with two TMTs. This design involved analysing, merging and interpreting data, first separately by data collection method and theme and then in a meta-interpretation. Lastly, there was a follow-up meeting for evaluating results.FindingsFindings from the study were that the methodology can be used to assess teamwork and sustainable quality culture, and the results also showed the strength of using two data collection methods to provide a broader picture of teamwork and sustainable quality culture. A follow-up meeting validated the results and provided additional value to the two TMTs in the form of suggestions on how to improve their teamwork and sustainable quality culture.Practical implicationsApplying this methodology can guide TMTs in how to improve their teamwork and sustainable quality culture within their organisations.Originality/valueThis is a new methodology, containing a developed questionnaire and an interview guide, aiming to assess and evaluate teamwork within TMTs and sustainable quality culture. The practice of the methodology adds value to both TMTs and their organisations, as well as provides a theoretical and methodological contribution to research on teamwork and sustainable quality culture.