The objective of the paper consists in finding out the factors of efficiency of the initial action stage in the mechanism of psychological support for leaders who have difficulty making decisions under uncertainty. The research methods are the analysis of literature, questionnaire survey, the survey itself, structured observation, gaming modeling of managerial uncertainty, control analysis of cases, experiment, qualitative analysis of graphically depicted data; Delphi method, and the statistical comparativecontrastive analysis of data using the non-parametric Mann-Whitney test of differences. Results of the research are as follows: the mechanism of psychological support is a self-developing open system whose forming elements are the psychologist's counseling performance, the event context of the uncertainty problem to be overcome, and the way the leader-client perceives the initiated by him process of counseling that develops in the course of receiving the support. The dynamically functioning structure of the mechanism of psychological support consists of four stages. It has been confirmed by experiment that counseling in the genre of client-centered approach combined with elements of cognitive-behavioral style is a factor of efficiency at the initial stage of action of the mechanism of psychological support for leaders. © 2019.