This investigation estimates a theoretical model that examines the influence of economic and non-economic satisfaction on formalization, specific investments, and dependence in B2B supply chain relationships from the sellers’ perspective. The study’s methodology is based on a deductive approach and data was collected using a structured questionnaire. The sample consisted of small and medium-sized companies across industries in Spain. The findings show that sales-specific investments rely on other business aspects than economic and non-economic satisfaction in B2B supply chain relationships, though a requirement is that the B2B supply chain relationships are marked by economic satisfaction. This research sheds light on antecedents of specific sales investments based on the perspectives of relationship marketing and transactional cost theories. In doing so, the study provides insights into the structural properties of economic and non-economic satisfaction, formalization, specific investments, and dependence in B2B supply chain relationships. Practical implications include the need for managers to ensure that their business partners are economically satisfied if they are to influence formalization in supply chain relationships. The importance of sales formalization is reflected in the positive relationship it has on specific investments in B2B sales relationships. The study’s value lies in the fact that it distinguishes between the role of two different types of satisfaction on formalization, specific investments, and dependence in B2B sales relationships. In so doing, the study helps determine the order of priority between economic and non-economic satisfaction to formalize and make specific investments in B2B sales relationships.