Awareness of mental events as mere representations rather than as accurate depictions of reality, also known as dereification, is one of the key features of mindfulness meditation. Dereification is juxtaposed to subjective realism, the process of being lost or totally immersed in the contents of one's mind. Excessive subjective realism is a hallmark of several psychiatric disorders. Here, we investigated whether a “mindful” (dereified) compared with an “immersed” (highly subjectively real) attitude, induced by instructions, differentially modulates approach-avoidance tendencies when processing visual stimuli. We presented novices and experienced meditators with neutral and attractive food images under both mindful and immersed states. Then, participants performed an approach–avoidance Task (AAT) during which we obtained behavioral data, salivary volume, EEG recordings, and self-report measures. The approach bias toward attractive food was correlated with N2 amplitude, a marker of response inhibition, and the regulation of this bias by the mindful instruction compared to the immersed instruction was associated with a modulation of the visual N1 amplitude, a marker of early selective attention. Individuals with more expertise in mindfulness meditation engaged in less late affective reappraisal during mindfulness than during immersion, as measured by lower amplitude in the late positive potential (LPP). Additionally, the ERPs sensitive to the AAT manipulation was also associated to self-report measures of subjective realism, food bias, and mindfulness meditation expertise but not to salivation measures. These findings provide novel insights into the mechanisms by which mindfulness-based interventions could be effective in a range of psychiatric conditions.