The aim of this study was to describe the process of creation and validation of methodology to assess the methodological quality of systematic reviews. From the expansion of the scope and addition of new items to the Assessment of Multiple Systematic Reviews (AMSTAR) instrument evidence of validity and reliability of the new methodology was sought. Firstly, the original scale was translated, adapted, expanded and evaluated by a panel of five experts. Then it was tested by evaluating a random sample of five systematic reviews by three judges with no formal training in the scale. Finally, the consolidated scale was assessed in a new panel by two judges. The panel of experts reached a consensus regarding the validity of the proposed changes. With respect to the scale total and per item score, the average agreement between judges was considered satisfactory in the consolidated scale. From the processes of adaptation and validation performed, the methodology in its final version consisted of 14 items that taken together indicate the methodological quality of systematic reviews from different areas of knowledge.