The goal of the present study was to characterize the assertive and non-assertive communications of a prekindergarten teacher and assess the relationship of such communications with the emotional climate of the classroom, specifically in terms of the quality of the relationships among the students. We analyzed 23 classroom observations carried out during the first period of a school year in a group of prekindergarten in a bilingual, medium-high socioeconomic level school. We collected data by means of non-participant observation and coded the information based on a a matrix we created to evaluate the teacher’s assertive behaviors and we used CLASS criteria to evaluate the emotional climate of the classroom. The results of the descriptive analysis of the data showed a positive relationship between assertive behaviors of the teacher and classroom emotional climate, and a negative relationship between non-assertive behaviors (ie, impositive and passive) and the emotional climate of the classroom. These findings are discussed in light of the implications of teacher communication style for building learning environments that promote the development of emotional and social skills of children at an early age.