Multicultural representation is a stated goal of many global scientific assessment processes. These processes aim to mobilize a broader, more diverse pool of information for international knowledge-building and synthesis processes while increasing social legitimacy and inclusiveness. Often, enhancing cultural diversity is encouraged through engagement of diverse expert teams and sources of knowledge in different languages. In this dataset, we examined the incorporation of multicultural diversity in the eight published assessments of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES). The culturally diversity of experts and knowledge holders participating in the process is not reflected in the assessment evidence base. Our results show that the IPBES assessment outputs are disproportionally filtered through English-language literature and authors from Anglophone countries. Some countries, such as the United States and United Kingdom, are over-represented compared to other countries, particularly in Africa and Asia, where English is a second or third language. Overlooking linguistic diversity can lead to incomplete and biased understandings of the drivers of and solutions to biodiversity loss.