Background: Dyspnea in obesity is common and dyspnea questionnaires are mostly validated for chronic respiratory diseases. The study aims to assess how modified Medical Research Council (mMRC) dyspnea scale correlates with post exercise dyspnea Borg scale in 6-minute walk test of the obese population. Methods: We performed a retrospective observational study on 342 obese patients with 6 MWT tests from February 2008 to November 2014 at a single tertiary hospital. Linear regression analysis was used to assess the relationship between mMRC and Borg dyspnea score. Fractional polynomial regression was used to analyze the relationship of mMRC and Borg scores with BMI. Results: MMRC dyspnea score was a strong predictor of post exercise dyspnea Borg score in the obese population in a univariate regression model (coefficient = 0.764, p ≤ 0.001). When adjusted to age, BMI, 6 MWT distance and PFT parameters in a multivariate regression model, the relationship remained statistically significant (coefficient = 0.587, p ≤ 0.001). The relationship was stronger in obese group with no airflow obstruction. Conclusion: In obese population, pre-exercise mMRC dyspnea score correlates significantly with post exercise dyspnea Borg score regardless of airflow obstruction. This is the first validity study regarding mMRC scale in assessing dyspnea in the obese population.