The paper presents the SEESG Model for sustainability assessment of companies using the composite indicator Corporate Sustainability Index (ICS), and their comparison in a case study. The composite indicator ICS is one of the options for constructing a benchmarking tool for comparing sustainability of companies in a given sector. The aim of this article is to compare manufacturing companies from different EU countries using the Sustainable Environmental, Social, Governance and Economics Model (SEESG Model) and a proposed composite indicator Index of Corporate Sustainability (ICS). The ICS integrates 16 economic and non-financial (environmental, social and corporate governance) performance indicators Iji, and is comprised of 5 sub-indices (economic sub-index ISEko1 Profitability; environmental sub-index ISEn1 Waste and Emissions and sub-index ISEn2 Resources consumption; social sub-index ISSoc2 Labour practices and Decent Work and corporate governance sub-index ISCg Monitoring and reporting corporate governance. Weights were determined by the PCA method. In the case study, six companies from the manufacturing industry from different countries were compared and the effectiveness of the composite indicator ICS in assessing sustainability was evaluated. Conclusions from the case study proved the suitability of the composite indicator ICS for comparing companies within the same industry, and for assessing corporate sustainability. For this reason, the SEESG Model for corporate sustainability assessment can be offered as a consistent and flexible model for investors. The use of the composite indicator ICS will make it possible for investors to integrate sustainability into their decision-making processes, achieve economic growth and help protect the environment as well as social values.