This paper highlights the main stages in developing a process of sustainability assessments in tourism (SAT) and applies a systematic literature review of empirical research based on pre-developed assessment categories. The aim is to characterise general approaches to measuring sustainability in tourism and to identify patterns and research gaps within these approaches. Four major assessment methodologies were identified through a hierarchical cluster analysis. Whereas new frameworks and indices explore new conceptual approaches to sustainability assessments, case studies and systems approaches rely on existing indicator work and create new assessment contexts. The literature review confirms the heterogeneity of these assessments, albeit without an overall sector-specific consensus. The results show that stakeholder involvement is not widely implemented in the indicator-selection process, and indicators are not linked to sustainability targets. The findings demonstrate that more effort is needed in relation to contextualising frameworks and assessment approaches, to foster target-oriented decision-making.