Background: The ecological validity of performance-based cognitive screeners needs to be tested in order for them to be fully recommended for use within clinical practice and research. Objectives: The objective of this study was to examine, within an Italian cohort of non-demented Parkinson’s disease (PD) patients, the ecological validity of the Montreal Cognitive Assessment (MoCA) by assessing its association with (1) functional independence (FI), (2) quality of life (QoL), and (3) behavioural-psychological (BP) outcomes. Methods: Seventy-four non-demented PD patients were administered the MoCA and underwent motor functional – i.e., Unified Parkinson’s Disease Rating Scale (UPDRS), Modified Hoehn-Yahr Scale (HY), and Schwab and England Scale (SES) –, behavioural and psychological – i.e., State- and Trait-Anxiety Inventory-Form Y (STAI-Y1/-Y2), Beck Depression Inventory (BDI), and Dimensional Apathy Scale (DAS) – and QoL evaluations – i.e., MOS 36-Item Short Form Health Survey (SF-36). Associations of interest against FI, QoL, and BP outcomes were tested via Bonferroni-corrected Pearson’s/Spearman’s correlations while covarying for demographics, disease duration as well as UPDRS-III, UPDRS-IV, and HY scores. Intake of psychotropic drugs was also covaried when assessing the association between the MoCA and BP/QoL measures. Results: MoCA scores were significantly associated with the SES (rs(73) = 0.34; p = 0.005) and the DAS-Executive (r(67) = −0.47; p < 0.001), while not to other FI/BP outcomes and QoL measures. Conclusions: The MoCA is a valid estimate of daily life functional autonomy in non-demented PD patients, also reflecting apathetic features of a dysexecutive nature.