Background: Pulmonary function test is essential to diagnosing and following respiratory diseases. Asthma-COPD overlap (ACO) patients commonly have a history of smoking exposure, lower lung function, impaired physical performance, and comorbidities characteristic of both Asthma and COPD. Aims: to evaluate the pulmonary function test for the first time in participants from ELSA-Brasil with self-report ACO. Methods: 174 participants from São Paulo City were enrolled during April-November 2022 (ELSA-BRASIL cohort study). Control (n=42), Asthma (n=42), COPD (n=49), and ACO (n=41) were defined by self-report at baseline. We evaluated pre and post-BD performance from FVC, FEV1, FEV1/FVC, and FEF25-75% spirometry parameters by KOKO system. In addition were applicated 36-Item Short Form Health Survey (SF-36 short), COPD Assessment Test (CAT), and WHO Quality of Life (WHOQOL-bref) questionaries. Results: Participants had similar demographic characteristics, with 56% women and a mean age of 64±9 years. The ACO participants presented lower FVC pre-BD values than asthma and COPD participants. In addition, for all other parameters, ACO participants showed lower values in both pre and post-BD tests (L and %) compared to other groups (Asthma and COPD). There were no differences in the SF-36 short, CAT, and WHOQOL-bref questionaries applied between Asthma, COPD, and ACO participants. Conclusion: ACO participants showed lower values in the spirometric performance test than asthma and COPD participants from the São Paulo investigation site of the ELSA-Brasil cohort study. Sponsorship: FAPESP (2018/02537-5, 2019/26449-0 and 2022/02510-5), LIM20-HC-FMUSP, CNPq (01 06 0115.00 SP).