Research in methodological quality (MQ) of prognosis studies (PS) is relevant in view of the important number of studies developed in this scenario. However, currently there are no instruments designed to measure MQ in PS, thus the aim of this study was to validate a scale to determine the MQ in PS. Scale validation study. Two independent researchers applied the scale (10 items/4 domains) in 119 articles found in 13 Journals of high, medium and low impact factor. Criterion validity was determined by contrasting MQ scores with Oxford Centre for Evidence-Based Medicine levels of evidence. Construct validity of extreme groups and high and low impact factors were estimated. Intraclass correlation coefficient was used to determine interobserver reliability, and the cut-off point was calculated using a ROC curve. The best cut-off point was 33, with an under curve area of 82.6 %. Criterion and construct validity were statistically significant with (p<0.001). Interobserver reliability was 0.91 and a scale to measure the MQ in PS was validated.