International Journal of Exercise Science 11(5): 609-624, 2018. An aversion to the sensations of physical exertion can deter engagement in physical activity. This is due in part to an associative focus in which individuals are attending to uncomfortable interoceptive cues. The purpose of this study was to test the effect of mindfulness on affective valence, ratings of perceived exertion (RPE), and enjoyment during treadmill walking. Participants (N=23; Mage=19.26, SD = 1.14) were only included in the study if they engaged in no more than moderate levels of physical activity and reported low levels of intrinsic motivation. They completed three testing sessions including a habituation session to determine the grade needed to achieve 65% of heart rate reserve (HRR); a control condition in which they walked at 65% of HRR for 10 minutes and an experimental condition during which they listened to a mindfulness track that directed them to attend to the physical sensations of their body in a nonjudgmental manner during the 10-minute walk. ANOVA results showed that in the mindfulness condition, affective valence was significantly more positive (p =.02, np2 =.22), enjoyment and mindfulness of the body were higher (p <.001, np2 =.36 and.40, respectively), attentional focus was more associative (p <.001, np2 =.67) and RPE was minimally lower (p =.06, np2 =.15). Higher mindfulness of the body was moderately associated with higher enjoyment (p <.05, r =.44) in the mindfulness but not the control condition. Results suggest that mindfulness during exercise is associated with more positive affective responses.