Background: Pneumonia caused by COVID-19 tends to be more severe in middle-aged and elderly individuals, often leading to decreased pulmonary ventilation function and negatively impacting quality of life post-recovery. However, studies on this topic are limited in Mongolia. Aim: To evaluate pulmonary ventilation function and exercise tolerance in middle-aged and elderly individuals after COVID-19 pneumonia. Materials and Methods: A hospital-based case-control study was conducted from June 2022 to December 2023 at Gurvan Gal United Hospital and the First Central Hospital of Mongolia. The study group included 65 individuals aged 50- 69 who had recovered from COVID-19 pneumonia, while the control group consisted of 65 age-matched individuals who had not contracted the infection. Participants underwent a questionnaire, spirometry, and a 6-minute walk test (6MWT) to assess lung function and exercise tolerance. Results: A total of 123 participants were included in the study. The study group showed a significant reduction in FEV1 (P=0.015). compared to the control group. However, no statistically significant differences were observed in FVC or the 6MWT results between the two groups (P=0.464). Symptoms such as chest pain, cough, fatigue, and insomnia were significantly more common in the study group than in the control group (P<0.0001). Conclusion Individuals aged 50-69 who had COVID-19 pneumonia exhibited prolonged symptoms such as persistent cough, chest pain, nasal congestion, sore throat, fatigue, and sleep disturbances at a significantly higher rate compared to the control group (P<0.0001). Pulmonary ventilation function showed a mild decline, with FEV1% being lower than in the control group (P=0.015). Additionally, pulmonary fibrosis was significantly more prevalent among the post-COVID-19 group compared to the control group (P=0.026).