This study aimed to investigate the relationship between primary school principals’ development based on self-determination theory and their conflict management styles. The population of the study was comprised of primary school principals in Sabzevar (Razavi Khorasan Province) in 2016-17 school year. These principals included 37 males and 37 females all of whom participated in the study based on total population sampling. The research instruments included Basic Psychological Need Satisfaction at Work Scale (Deci et al., 2001) and Conflict Management Technique Scale (Robbins, 1991). The content and face validity of the instruments was confirmed by experts and their reliability was calculated to be 0.90 and 0.81 respectively by the use of Cronbach’s alpha. Descriptive and inferential statistics including the Pearson correlation was used to analyze the data. The results demonstrated that there was a significant relationship between school principals’ development and conflict management styles. More specifically, the higher the female principals’ development, the higher their use of competing, avoiding, and compromising management styles. Nonetheless, there was no a significant relationship between female principals’ development and other conflict management styles. In addition, there was a significant relationship between male principals’ development and all conflict management styles. The higher the male principals’ development, the more frequent their use of the conflict management styles.