Negotiation is an action that people engage in daily, from a very young age, and in the business world, it holds particular importance for the success of operations. The selection and application of valid strategies, tactics, and techniques in negotiation greatly contribute to the success and positive outcome of negotiations. Building strong relationship plays a crucial role in the successful process of business negotiation. This paper explores the significance of developing positive relationships between negotiators as a key factor in achieving mutually beneficial agreements. Through carefully selected communication strategies, emotional intelligence and mutual understanding, business negotiators can create an environment of trust and collaboration, significantly enhancing negotiation outcomes. The purpose of this paper is to investigate the extent to which emotional intelligence and communication skills impact the establishment and maintenance of business relationships. The paper delves into the strategies, tactics and techniques of business negotiation, as well as the concepts of emotional intelligence and communication skills . The empirical part of the study is based on secondary research of a negotiation case between two large companies. The research was conducted using a case study approach and relevant articles on the topic. The paper presents two hypotheses, and both are accepted. Through a case analysis, it is shown how insufficient use of emotional intelligence and communication skills led to the deterioration of partnership relations that had been built for years. Emotional intelligence, as well as well-developed communication skills, greatly influence the establishment and maintenance of partnership relations.