Negotiation is a key factor in business processes because it enables a company to achieve successful business results. Successful negotiation is an essential condition for achieving business goals. This master's thesis examines the influence of personality traits as determinants of successful negotiation in the real estate market of the City of Zagre, it seeks to explore the impact of negotiators' personality traits on achieving successful negotiations in the sales process. As the real estate market is very dynamic, sales processes in it are specific, and negotiation is one of the key factors for successfully concluding a sales transaction. In addition to allowing the real estate agent to acquire material goods to ensure their livelihood, it grants them a certain position in society, serves as a source of social contacts and relationships, can help them in realizing their own abilities and potentials, and can be a source of personal satisfaction or frustration. The theoretical part of the paper covers the definition of basic concepts from the world of negotiation and mediation in real estate trading. Also, strategies that negotiators can use to enhance their skills are discussed. Research is conducted to determine how the connection of the Big Five personality traits affects the effectiveness of negotiations, namely the success of the sales process of agents in the real estate market of the City of Zagreb.