Internalizing disorders are among the most frequently diagnosed psychological problems in childhood (Crawford, Schrock, & Woodruff-Borden, 2011). Evidence suggests that children who have the tendency to avoid, and less developed effortful control, are more likely to develop symptoms of internalizing (White, McDermott, Degnan, Henderson, & Fox, 2011). Similarly, preschoolers who are rated as being more withdrawn during social interactions often display more social anxiety than less avoidant peers (Ale, Chorney, Brice, & Morris, 2010). Furthermore, more difficulty with emotion understanding, and social avoidance, has been shown to directly relate to internalizing problems such as depression, fear/anxiety, somatic complaints, worry and rumination (Rieffe & De Rooij, 2012). Although researchers have identified some early vulnerability factors that lead to the development of internalizing problems, research on anxiety/internalizing in the preschool age population is scarce (Wichstrom, Belsky, & Berg-Nielsen, 2013). The current study sought to fill this gap in the existing literature. The study sample consisted of 139 parent, teacher, and preschooler participants from a university setting (38 to 82 months old; with a mean age of 57 months). Temperament was examined through parent ratings on the Structured Temperament Interview (STI) (Teglasi, 2009) and the Children's Behavior Questionnaire (CBQ), Short Form (Putnam & Rothbart, 2006). Emotion understanding was examined by preschoolers' performance on the Emotion Comprehension Test (ECT) (unpublished). Internalizing behaviors were measured through teacher ratings on the Social Competence and Behavior Evaluation (SCBE) (LaFreniere & Dumas, 1996). Correlations between the STI factors and CBQ scales illustrated underlying aspects of emotionality and reactivity that influence children's approach/avoidance tendencies, and the link between temperament and overall adjustment. Children who were rated high on preferring familiar/routine activities were also rated as having more internalizing problems, and worse performance on a measure of emotion understanding; whereas, children who were rated high on sociability were rated as having fewer internalizing problems. Regression analyses demonstrated that effortful control moderated the relationship between sociability and internalizing behaviors such that children with high sociability and high effortful control displayed the best behavioral adjustment; and children with low sociability and high effortful control displayed the most internalizing behaviors.