Dynamics and interactions among different stakeholders in their objectives, priorities, and potential tensions within relationships make it even more challenging to successfully achieve the outcomes of sustainability initiatives and meet or exceed stakeholder expectations. Therefore, it is crucial to design evaluation or impact assessment processes to determine how different stakeholder groups understand, engage with, and are affected by the progression and implementation of specific sustainability initiatives (e.g., environmental, economic, and social). This requires a decision-making process that involves proactive analysis and assessment to identify and understand the potential positive and negative impacts on stakeholders, the environment, and society. Furthermore, it is necessary to develop strategies that address stakeholders’ concerns and expectations while simultaneously achieving sustainable development goals. Finally, such decisions will have various implications for decision making, and various trade-offs need to be made, and optimizing the potential synergies are needed. The objective of this chapter is to examine the stakeholder impact assessment process, particularly within the context of relationship-oriented sustainability marketing. By adopting an impact assessment process that integrates systems theory and conceptualizations of complex network relationship management, we aim to demonstrate that it is conceivable to measure firms’ effectiveness using a range of indicators for the Sustainable Development Goals (SDGs). At the same time, this approach facilitates the achievement of relationship management objectives necessary for relationship-oriented sustainability marketing.