ABSTRACT YouTube unboxing videos have become a popular genre among youth, and hosts often receive financial or other incentives for showcasing products. Although sponsored relationships must be explicitly disclosed per legal regulations, not all videos comply. This study assesses US tweens’ reactions to unboxing videos with varying cues of a sponsored relationship between the host and product manufacturer, using a 3 (sponsored; non-sponsored; sponsorship unaddressed cue) x 2 (advertising training; no advertising training) randomized experimental design. The sample consisted of 215 tweens between ages 8–13 years. Half of the participants were randomly assigned to watch an advertising literacy training video before the unboxing video. Tweens detect a higher selling intent within the sponsored video (relative to the non-sponsored video), only after viewing the advertising literacy training video. The training video enhances the positive relationship between perceived informative intent and purchase intention, while weakening the positive relationship between perceived selling intent and purchase intention. Findings suggest tweens may have a unique mental schema for unboxing-style online videos which is a hybrid of informational and advertisement. Brief training videos could be used on video streaming platforms to develop and cue tweens’ advertising literacy.