Objective: To translate into Spanish and analyze the evidence of validity based on the content of the items in the brief version of the Mindful Attention Awareness Scale of 5 items (MAAS-5). Method: An instrumental study that involved the translation to Spanish of the items of the short version of the MAAS-5 scale, using the back-translation procedure. We analyzed the evidence of validity based on the test content, with the participation of a total of 14 expert judges. The degree of clarity, coherence and relevance of the items was quantified using the Aiken V coefficient and their 95% confidence intervals using an ad hoc template developed in the MS Excel program. Results: The items of the MAAS-5 show favourable evaluations of their clarity, coherence and relevance, where all the values of V were statistically significant and greater than 0.70. On the other hand, the lower limit of 95% confidence intervals of all the items satisfies the criterion at population level (Li˃0.59). Conclusion: The empirical evidence of validity based on the test content of the MAAS-5 reports that all are sufficiently relevant, coherent and clear to adequately represent the construct mindfulness, both at sample and population level. This suggests that the MAAS-5 can be a brief and useful measure to assess mindfulness. On the other hand we suggest carrying out further studies that analyze other sources of evidence of validity of the MAAS-5.