Environmental sustainability boundaries can help us navigate a sustainable development trajectory, by evaluating environmental performance of current actions in relation to such boundaries. However, current definitions of environmental sustainability boundaries have shortcomings when used in environmental assessments. The shortcomings include considerations of regional differentiation and transparency with respect to how uncertainty is addressed. This paper seeks to improve the definition and application of environmental sustainability boundaries in environmental assessments by reviewing existing approaches to set them and elaborating an analytical framework for defining, communicating and adopting environmental sustainability boundaries in assessments. 110 original environmental sustainability boundaries were identified from existing literature and grouped into 13 categories of boundary approaches. The framework addresses five components (objective, boundary principle, uncertainty principle, accepted levels of impacts, and scientific estimate), and recommends practices for each. The framework is recommended for defining, communicating and adopting environmental sustainability boundaries, to facilitate a consistent application of them in environmental assessments. The analysis of existing boundary approaches showed that they often handle value-based aspects (e.g. choice of uncertainty principle) differently. Thus, it is recommended that value-based aspects are communicated explicitly to enable a practitioner to consider how this resonates with his/her own values or the values of central stakeholders when adopting environmental sustainability boundaries in an environmental assessment.