Objectives <p>Two studies examined whether brief mind-body interventions could improve mood and influence state mindfulness. Exploratory analyses investigated state mindfulness and state self-compassion as potential mechanisms of action.</p> Method <p>Both studies randomly allocated participants to one of three conditions: mindfulness, progressive muscle relaxation (PMR), or active control. Study 1 was conducted online (<i>n</i> = 57), and Study 2 was lab-based (<i>n</i> = 98). Each study was a single-session experiment with short intervention exercises (18–20&#xa0;min).</p> Results <p>Negative affect decreased after the intervention (Study 1: <i>p</i> &lt; 0.001, <i>ηp</i>² = 0.24; Study 2: <i>p</i> = 0.01, <i>ηp</i>² = 0.06). In Study 1, after recalling a painful or difficult situation, positive affect increased (<i>p</i> = 0.02, <i>ηp</i>² = 0.09). In Study 2, where no mood manipulation occurred, a reduction in positive affect post intervention was found (<i>p</i> &lt; 0.001, <i>ηp</i>² = 0.19). In both studies, only the mind-body interventions led to increases in state mindfulness (all <i>p</i> &lt; 0.01). Increases in state mindfulness were related to increases in positive affect in both studies (<i>r</i> = 0.27 to 0.40, all <i>p</i> ≤ 0.01). Increases in state self-compassion were also related to increases in positive affect in Study 1 (<i>r</i> = 0.57, <i>p</i> &lt; 0.001).</p> Conclusions <p>In both studies, changes in mood were not specific to the mind-body exercises; audiobook readings also had an effect. The improvements in state mindfulness and links to positive affect suggest state mindfulness may be a mechanism of action. Future research should interrogate these findings using theoretically based and adequately powered studies.</p> Preregistration <p>This study is not preregistered.</p>