The topic of this thesis are Defence mechanisms in business communication. They are useful in everyday life, in private as well as in business environment due to large amounts of stress and unpleasant situations that could possibly happen. The research that is carried out in this thesis is secondary, respectively the research of theory. The goal of researching the theory of this topic is to find out the effect the mechanisms have on people and their effect in the business environment. Misunderstanding of the defence mechanisms could have a negative impact on the quality of business communication. It is a hypothesis with which you start a research. Due to misunderstanding the defence mechanisms and the usage of unripe ones, people could put themselves in unpleasant situations where they seek to find guilt in others or direct their anger at the wrong people. Such usage of mechanisms creates foul business communication and the hypothesis itself is confirmed in conclusion.