This study was carried out to investigate the relationship between mothers’ emotional intelligence, resilience, and positive thinking and preschoolers’ separation anxiety. The research design was descriptive, correlational. The statistical population of the study comprised 310 preschoolers attending child care centers in Sari. The sample size was determined to be 150 based on Krejcie and Morgan Table and the sample was drawn through random cluster sampling method. The instruments included Conner-Davidson Resilience Scale (2003), Emotional Intelligence Scale (Schutte et al., 1998), Oxford Happiness Inventory (Argyle et al., 1989), and the Preschool Anxiety Scale (PAS). The obtained data were analyzed via pearson correlation and regression analysis (enter method). The results showed that mothers’ emotional intelligence (and its different dimension such as emotion perception, managing emotions, utilizing emotions), resilience, and positive thinking were negatively associated with children’s separation anxiety. In addition, emotional intelligence, resilience and positive thinking are good predictors of separation anxiety of preschool children. Moreover, a significant share of variation in preschoolers’ separation anxiety has been explained by emotion perception, managing emotions, resilience, and happiness. According to the final model, managing emotions, emotion perception, resilience, and positive thinking were respectively the most effective factors in reducing children’s separation anxiety.