Background/Objectives: Respiratory dysfunction in Parkinson's disease (PD) is a clinically relevant but frequently underrecognized manifestation associated with functional impairment and increased risk of respiratory complications. This study compared spirometry and impulse oscillometry (IOS) in the assessment of respiratory function in PD, with particular focus on the detection of subtle or peripheral airway abnormalities. Methods: A prospective, single-center, cross-sectional study was conducted, including 108 participants (55 patients with PD and 53 control subjects). Pulmonary function was evaluated using standardized spirometry and IOS protocols. Group comparisons were performed using non-parametric tests, while multivariable regression analyses adjusted for potential confounding factors, including age, body mass index, smoking status, pollutant exposure, and cardiovascular comorbidities. Results: IOS identified a higher frequency of abnormal categorical findings compared with spirometry, including among subjects with normal spirometric values. Although dyspnea was more frequent in patients with PD in unadjusted analyses, multivariable regression demonstrated that PD was not an independent predictor of respiratory dysfunction. Pollutant exposure was significantly associated with abnormal IOS findings (p = 0.011). No significant differences were observed between PD and control groups regarding continuous spirometric or oscillometric parameters. Only a weak association between disease severity and FEV1 (%) was identified, whereas no significant correlations were observed for oscillometric parameters. Conclusions: IOS may provide complementary information regarding subtle or peripheral respiratory abnormalities in patients with PD. The findings suggest that respiratory alterations in this population are likely multifactorial and not independently determined by PD itself. Incorporating oscillometric assessment into respiratory evaluation may contribute to the identification of subtle respiratory mechanical alterations in patients with PD.