Multisectoral groups and holding companies have been operating in dynamic and complex business environments, with increasing concerns to reach higher levels of sustainability. On the other hand, the G4 Guidelines published by the Global Reporting Initiative (GRI), which are the most widely used organizations worldwide for the preparation of their sustainability reports, do not provide guidance supplements for multisectoral groups. In this context, this dissertation aims to propose a model for the sustainability performance assessment of multisectoral business groups by integrating the GRI G4 Guidelines with the Balanced Scorecard tool, with support of multicriteria decision making methods. The research can be considered descriptive, methodological and applied. Based on the results of the bibliographic and documentary review on the central themes of this research, a conceptual model was developed for assessing the sustainability performance of multisectoral groups (MSGs), aiming to fill gaps identified during the literature review and documentary analysis covering the period 1988-2018. The applicability of the model could be demonstrated through an empirical study in the Algar Group, which operates in ICT, agribusiness, tourism and services sectors. The results of this research can be replicated in processes of sustainability performance assessment of other multisectoral groups in Brazil and abroad. Within the scope of the GRI methodology, they can contribute to the formulation of a guidance supplement addressed to multisectoral groups, i.e. the G4 Multisector Disclosures.