Aim: To describe processes for the adoption of trastuzumab in four countries in the use of health technology assessment (HTA): Poland, Albania, Brazil and Colombia. Materials & methods: Mixed methods were used for collection and triangulation of data. Data were examined following a conceptual framework connecting HTA process steps and key principles. Results: Trastuzumab was generally assessed following well-structured HTA processes. Nonetheless, areas of improvement were detected in terms of transparency and inclusiveness, as well as in methods used. The extent to which different criteria influenced decisions was unclear. Conclusion: This study covers an area in which information may not always be available, and sets the example for emerging countries interested in HTA. Further studies to gain a better understanding on decision-making across settings are warranted.