The role of preschool teachers in supporting children’s language development is unquestionably substantial. To ensure the quality of preschool teachers’ performance in this specific task, various assessing instruments have been developed and justified in recent years. This study joins such efforts by investigating a new scale based on the “Framework for assessing preschool teacher competence in promoting children’s language development” proposed by a previous research. The scale’s psychometric properties are examined with a sample of 685 Vietnamese preschool teachers. The results supported the four-factor model suggested by the original authors and confirmed its reliability and validity. Finally, further usages of the scale are discussed.