The world is aging and experiencing loneliness. Functional impairment in instrumental activities of daily living (IADL) in older people (OP) with mild neurocognitive disorder (MNCD) predicts loneliness. After the pandemic, there was an increase in perceived loneliness. We explored the association between loneliness, depression, deficits in IADL, and cognitive symptoms among OP. From February to December 2023, using a cross-sectional design, we interviewed probable cases with mild cognitive impairment and caregivers in two public facilities. We administered the UCLA Loneliness Scale v3, Lawton IADL Scale, Mini-Mental State Examination (MMSE), and Yesavage’s Geriatric Depression Scale. Samples were matched: 85 per group, 82.4% were women, married (52.95%), and mean age of 69.17 (±6.93) years. In our study, 30% displayed moderate to high levels of perceived loneliness. Multivariate analysis showed loneliness was associated with depression, low levels of IADL, and older age, but not with cognitive symptoms, which explained 22% of the total variance (F 165) = 16.99, (p < 0.001). Targeting symptoms and behaviors that could be modified (i.e., depression and functionality) can improve feelings of perceived loneliness and have an impact on morbidity and mortality with which it is associated.