The practice of mindfulness involves the training of the processes involved in the self-regulation of attention. Attentional flexibility, as opposed to mental rigidity, is one of the main cognitive skills enhanced by the practice of mindfulness. In psychology, the Einstellung effect refers to the fact that individuals automatically apply old, known strategies when solving a problem, even though new strategies might enable them to solve it more efficiently. This phenomenon reflected mental rigidity that could be measured by the Water-Jar Task (WJT) [13]. Previous experiments have shown that meditators who have practiced mindfulness regularly for several years were less susceptible to this phenomenon, revealing less mental rigidity [5, 15]. Following these experiments, we investigate the effect of brief mindfulness training (10 min) on mental rigidity, by replicating the WJT protocol used by Greenberg et al. [5] on 62 participants split into two groups. The mindful group was trained in mindfulness meditation and the control group listened to a podcast on the topic of meditation just before the task. Given that brief mindfulness training improves insight problem-solving, we can speculate that it might also reduce cognitive rigidity via increased attentional flexibility. So, we hypothesize that the mindful group will obtain a lower score of cognitive rigidity than the control group. The results showed that brief mindfulness training and trait mindfulness reduce the cognitive rigidity score on the WJT. These findings support the idea that mindfulness could contribute to de-automating certain cognitive processes and increase creativity.