In a competitive business world, brands and products are essential to a company's success and growth. It is important for any business that wants to succeed in international markets to understand how valuable these elements are and how to manage them effectively. Rebranding and product launch strategies emerge as tools for companies looking to stay ahead in the global marketplace. Rebranding helps companies maintain relevance in changing markets, while introducing new products is important for addressing shifting customer needs. However, both have significant risks and costs, as many rebranding efforts fail to resonate, and new products often struggle to gain market acceptance. Given the importance of these strategies, understanding how new brands and products gain legitimacy—particularly in international markets—is essential. This doctoral thesis explores the process of legitimation, which is crucial for acceptance among various stakeholders, and addresses the research question: “How do companies legitimize new brands and new products in international markets?”. To answer this main research question, this thesis focuses on five papers. Paper I provides a review of international branding literature, identifying research gaps and suggests scholars to explore branding dynamics in emerging markets and B2B contexts. Paper II focuses on the challenges of internal and external legitimation in the rebranding process in developed and emerging markets. Paper III identifies the brand knowledge dimensions that matter most to different stakeholders during the rebranding process. Paper IV examines the factors influencing new product launches across various institutional contexts, presenting a typology that highlights the roles of brand awareness and price sensitivity. Paper V focuses on the relationship between internal and external challenges in emerging markets, proposing strategies to address these challenges effectively. By integrating institutional and legitimation theories with rebranding and product launch strategies, the thesis offers insights and practical guidance for businesses operating in global markets. The findings help understanding the complexities of legitimation in different contexts and provide actionable strategies to enhance the acceptance of new brands and products internationally.