Despite the efficacy of mindfulness-based interventions for a wide range of psychological problems, their mechanisms remain unknown. Analogue studies of key treatment components can help distinguish these approaches. One such component, focused-breathing meditation, has rarely been studied in direct comparison to another active and theoretically distinct technique, cognitive reappraisal. The present study examined the effects of mindful breathing and cognitive reappraisal instructions on negative affect and executive control, two potential mechanisms of mindfulness, in a laboratory setting. Non-clinical college undergraduates (N = 136) were randomly assigned to a 10-minute mindfulness, reappraisal, or mind-wandering control condition. Contrary to hypotheses, no between-group differences were found in sadness ratings, state mindfulness, or the inhibitory control dimension of executive control following the intervention. The mindfulness condition showed lower inattention compared to the mind-wandering condition. Implications of these results are discussed in terms of specific theoretical mechanisms of mindfulness- and cognitive-reappraisal-based interventions.