<p>Art viewing has been associated with well-being and positive mental health, yet its benefits are not universal across contexts or viewers. A key question is which aspects of art-viewing experiences drive beneficiary effects and whether they can be directly augmented to enhance well-being. To answer this question, this study explored the well-being effects of two art-based theory-informed augmentation videos at the National Gallery, London: one providing guided viewing instructions focused on style and slow, detailed observation, and the other offering a pre-viewing mindful breathing session. In the first large (<i>N</i> = 281) pre-registered study, we compared augmentation videos to a standard gallery visit. Further, in a laboratory-based follow-up (<i>N</i> = 33), we compared one pre-viewing intervention with a filler free-writing task to isolate the potential effects of the video strategy. Both studies used mixed-methods randomised controlled trial designs. Across conditions and studies, significant improvements in well-being were detected from pre- to post-gallery viewing. However, the overall effect of either video intervention did not enhance the art-viewing experience or lead to greater well-being changes. Rather, we found that guided viewing led to greater increases in positive mood than pre-viewing mindfulness and that, among first-time visitors, such strategies may be especially beneficial. We interpret the findings in the context of prior mixed evidence and suggest that future research should adopt a more holistic approach that incorporates multiple interacting mechanisms and more systematically investigates the role of our moderating variables.</p>