The project investigates the determinants of micro, small, and medium-sized enterprises (SMEs) internationalization and their sustainability in the post-COVID era. The aim is to identify the key factors that influence the internationalization of SMEs, including financial performance, marketing strategies, CSR, and innovation. The research will compare attitudes and processes before and after the COVID-19 pandemic. A questionnaire survey conducted among Czech SMEs compares the individual determinants of internationalization for domestic SMEs and those with activities abroad. The project offers opportunities for cooperation with companies, institutions, and organizations focusing on promoting SME internationalization and sustainability, thus contributing to economic development and competitiveness.