Abstract This thesis investigates how the composition and diversity of corporate alliance portfolios influence firms’ environmental performance, with a particular focus on the Electrical and Electronic Equipment (EEE) sector. As sustainability has evolved into a central strategic objective for companies worldwide, profitability alone is no longer sufficient to define competitiveness. Firms are now evaluated not only on financial metrics but also on their environmental and social impact, as growing regulatory pressures and stakeholder expectations demand measurable commitments toward sustainable development. Addressing complex challenges such as decarbonization, circular economy, and eco-innovation increasingly requires collaboration rather than isolated corporate action. In this context, managing sustainability-oriented alliance portfolios has become a crucial means of accessing complementary knowledge, technologies, and resources that foster innovation.