Rapidly developing digital technologies affect private companies' digital transformation (DT). However, most companies have not made progress in DT as they initially expected. While it is claimed that employees' mindset is critical in promoting DT, there is a paucity of empirical research documenting how their mindset is related to progress in DT. This study presents a new concept of the digital growth mindset, which is the belief that digital technology can improve people's abilities. Employees with this mindset embrace new technologies proactively, which enhances their agility in changing environments, increasing their engagement in DT. A questionnaire survey conducted in Japan showed that digital growth mindset positively affects employees' DT engagement and digital agility.