Health-related quality of life (HRQoL) is an important outcome from the perspective of boys with haemophilia and their parents. Few studies have captured the HRQoL of boys with haemophilia in developing countries. This article reports on the cross-cultural adaptation of the Canadian Haemophilia Outcomes – Kids Life Assessment Tool (CHO-KLAT) for use in São Paulo, Brazil. The CHO-KLAT2.0 was translated into Portuguese, and then translated back into English. The original English and back-translation versions were compared by a group of three clinicians, whose first language was Portuguese. The resulting Portuguese version was assessed through a series of cognitive debriefing interviews with children and their parents. This process identified concepts that were not clear and revised items to ensure appropriate understanding through an iterative process. The initial back-translation was not discrepant from the original English version. We made changes to 66% of the CHO-KLAT2.0 items based on clinical expert review and 26% of the items based on cognitive debriefings. In addition, two new items were added to the final Portuguese version to reflect the local cultural context. The final result had good face validity. This process was found to be extremely valuable in ensuring the items were accurately interpreted by the boys/parents in São Paulo Brazil. The results suggest that professional translators, clinical experts and cognitive debriefing are all required to achieve a culturally appropriate instrument. The Portuguese CHO-KLAT2.0 is well understood by Sao Paulo boys/parents. The next step will be to test its validity and reliability locally.