The vast majority of studies investigating the relationship between dairy working and respiratory impairments are cross-sectional and longitudinal studies are scarce. The present study aimed to assess respiratory impairments and risk factors in a group of dairy workers in a modern livestock complex. Ninety-six male dairy workers and 87 sex-matched referent workers were studied. Pulmonary function parameters were derived from the workers’ medical records. Respiratory symptoms were assessed using the European community respiratory health survey questionnaire. The workers’ exposure to bioaerosols was also assessed. The majority of dairy workers (93.8%) were never smokers. The means of all pulmonary parameters were significantly lower in the dairy workers than in the referent group. A significantly higher prevalence of shortness of breath (17.7%), wheezing (15.6%), and chest tightness (13.2%) was observed in the diary workers than in the referent group. Exposure to dairy pollutants, duration of exposure, smoking, overweight, and obesity were significant predictors of impaired pulmonary function. Dairy farming was associated with reductions in pulmonary parameters with a pattern consistent with obstructive ventilatory disorders. Significant reductions in VC (–0.98; P<0.001), FVC (–0.38; P<0.001), FEV1 (–1.28; P<0.001), FEV1/FVC (–1.10; P<0.001), and PEF (–0.49; P<0.001) by one-year increment in the duration of exposure were observed.