The study of personality has always been presented in Psychology as a way to understand the individual's behavior and characteristics. Within such context, several theorists deepened their studies and used techniques to reveal the psychical world structure. By attempting to know the individual in their characterological profile, the psychologist and educator Helena Antipoff decided to revive her experience in the former Soviet Union by means of the observation models developed by the psychologist and psychiatrist Lazursky. When Antipoff arrived in Brazil in 1929, invited by the government to assist in the development of the educational reform in the period called New School, she started to spread Lazursky's work in the state of Minas Gerais. Antipoff used Lazursky's Natural Experimentation rather than intelligence tests in psychological evaluations as a method aimed at the characterization of personality through observations of the behaviors and routine under natural conditions. She researched about individuals by using systematized and standardized observations and experiments, whose results were analyzed methodologically in figure and tables, which helped her study the personality of both the students and teachers. The purpose of this paper is to show, based on primary source documents from Antipoff's publications between 1930's and 1950's, the study of the personality through the Natural Experimentation method as the main model for the beginning of her educational work in Brazil. The use of the method contributed to the new educational structure, once it consisted of investigating and evaluating the student according to his profile, that is, his personality.