Background: This research was conducted to objectively evaluate the level of brain fog that may develop due to many reasons. Methods: This was a methodological study. This study was conducted between April and May 2021 in Turkey. Content validity ratio, Exploratory Factor Analysis, Confirmatory Factor Analysis, Kaiser-Meyer-Olkin analysis and Bartlett’s test of sphericity, Item analysis, Cronbach’s alpha coefficient, Spearman-Brown, Guttman Analysis and test-retest correlations validity-reliability analysis were performed. The statistical meaningfulness level in all tests was determined as p<0.05. Results: As a result of context validity, factor analysis and item analysis, a 30 item scale with 3 subscale was obtained. In the scale, the variance amount explained by the three sub components was on a very good level (77.43%). The fact that all of the Cronbach alpha, Spearman-Brown and Guttman internal consistency coefficients of the scale and all of its subscale are above 0.70. When the test retest reliability coefficients of the scale was examined, the scale was found to present consistent results in different applications and the scale was found to be reliable with regard to the constancy coefficient. Conclusion: The Brain Fog Scale consists of 30 items and three subscales. It is a valid and reliable instrument that is appropriate for Turkish society. It can be used to determine the level of brain fog in the last 30 days.