According to the findings of several studies, parents' assessments of their toddler's language are valid and reliable evaluations of children's language competence, especially at early development stages. This study examined whether preschool teachers, who spend a relatively great deal of time with toddlers in various preschool activities and engage in diverse social interactions with them, can also validly assess their language competence. The purpose of this study was to examine the degree of agreement between parents' and preschool teachers' assessments of toddler language competence. In addition, the study sought to establish whether toddlers' gender and parental education have any significant effect on parents' and preschool teachers' assessments of toddler language competence. The sample included 140 toddlers aged 16- to 30-months-old that had attended preschool for at least one year. The parents and preschool teachers assessed toddler language competence independently using the "Communicative Development Inventory for Toddlers 16 to 30 Months Old" (Marjanovic-Umek et al. 2008b). The findings showed a low to moderately high correlation between parents' and preschool teachers' assessments of various areas of toddlers' language (e.g. vocabulary, mean length of utterance, and sentence complexity). Preschool teachers assessed toddler language competence lower in all areas than parents did. The results also showed that parental education and toddlers' gender had a significant and high impact on parents' assessments of their toddlers' language competence. The results obtained were interpreted from the perspective of the opportunity to include parents and preschool teachers that accompany toddlers in various social contexts in assessments of toddlers language, and from the perspective of parents' and preschool teachers' implicit theories on language development, also in connection with toddlers' gender and parental education. (Contains 1 note, 5 tables, and 2 figures.)