The relevance of the study is due to the fact that the BRICS (Brazil, Russia, India, China, South Africa) countries have a huge potential for the development of innovative business. The purposes of the study are to analyse the specifics of the organisation of startup projects in some BRICS countries, to identify key differences in approaches to their development, and to assess the impact of the economic environment and government initiatives on the formation of an innovation ecosystem. To achieve these purposes, the authors of the article have performed the following objectives: the basic concepts related to startup entrepreneurship, their classification and differences are identified; the regulatory framework governing the activities of startups in some BRICS countries is analysed; the available financing mechanisms for the startups, including government programmes, venture funds, grants and private investments, are identified; the current economic situation of the studied states and its impact on the development of innovative entrepreneurship are considered; a comparative analysis of startup organisation models in selected BRICS countries has been conducted, and their strengths and weaknesses have been identified. The structure of this article includes two research sections. The first one examines theoretical and legal aspects of the startup entrepreneurship, regulatory framework, and financing mechanisms. The second section considers the economic situation in the BRICS countries, assesses its impact on the startup ecosystem, and provides a comparative analysis of startup development models. The work is completed with detailed conclusions on the conducted research.