This research analyses the contents of the videos of the ten Spanish children’s YouTube channels with the highest number of followers and video plays to identify correlations between the thematic axes of the videos and the increase in digital engagement data. Little is known about the topics that the most popular Spanish-language YouTube influencers share with preteens and young adults’ audience. In response, this exploratory study will use content analysis to examine this gap and contrast the themes that its videos reflect against others. For this purpose, interpretive-based content analysis is carried out based on an analysis sheet validated by expert judgment. Among the main results, it is shown that most of the children who are the lead character of the channel are currently between 10 and 12 years old, having created the channels an average of five years ago, which shows how early many YouTubers are starting in this industry. There are also differences in the thematic axes of the channels’ videos according to the gender of the children’s influencers, with a higher representation of male YouTubers devoted to gameplays, while their female peers have a more significant presence in videos in the lifestyle category. It is concluded that there is a need to supervise the contents accessed by children on this platform since it can deepen not only gender gaps but also become a wrong reference of role models.