The study attempts to analyze the implications of the war in Ukraine for the issues of development and inequalities in the BRICS block. The so-called “emerging economies” play an essential role in the global system, both in economic and political terms. The article compares the political and economic backgrounds of Brazil, Russia, India, China, and South Africa, their development, the “status quo” and their future aspirations, and analyses how the war in Ukraine may change the global development scenario. It is essential after the BRICS summit in South Africa invited six new members to the group. The article is rooted in complexity theory, supported by a mixed methodology approach. We show how the given research methodology, informed by complexity theory, can furnish new insights into global sustainability. The statistical method was used to gauge the correlation-regression impact of inequalities in BRICS countries on their sustainable development. The analysis allows several conclusions to be ventured: sustainable development is closely linked to inequalities and vice versa; the war has had a significant, multidimensional impact on the development paths and inequalities in the BRICS countries, which potentially could worsen, and the war is a major shocking event that can lead to global system changes and implications which are broader than merely for the subregion.