Background Mindfulness based interventions (MBI) are becoming increasingly popular. Given their nature (i.e., training of focused attention and cognitive control), efforts have been made to study their potential benefits to different aspects of cognition, resulting in mixed results. In light of the inconsistent findings, concerns regarding the methodological quality of such studies, and recent surge in randomized controlled trials of mindfulness interventions, we conducted a meta-analysis focused on MBIs effects on attention, working-memory and executive control in healthy adults. Methods We limited the included studies to randomized controlled trials of mindfulness-based interventions in healthy adults, resulting in 27 included studies (N = 1632). Results We found an overall effect of g = 0.2, with significant effects on attention (g = 0.18) and executive control (g = 0.18), but not on working-memory. Moderation analyses showed that the type of control group included in the study or the dosage (total hours of intervention) did not modulate these effects, but the number of in-class sessions did: the more sessions, the stronger the effect. Conclusions MBIs have limited positive effects on attention and executive control in healthy adults. More studies are needed to address how participants’ motivation may account for this effect, and clarify whether the smaller effects we found are due to our focus on healthy adults, or due to overestimation of effect sizes in previous meta-analyses.