Objectives Loneliness adversely affects the prognosis, treatment, and remission of late-life depression. However, no clear distinction of the cause or definition of loneliness was imposed in existing literatures, resulting in mixed findings of the effect of loneliness to late-life depression (LLD). The aim of this study was to explore the association between different facets of loneliness and risk factors of LLD, specifically, if age of onset in LLD possess a different clinical profile in the clinical group. Method 101 Chinese patients with depression and 81 healthy elderlies aged 60 or above were assessed on loneliness level, depressive symptoms, cognitive symptoms, physical condition, and motivational level. Univariate analyses were applied in exploring group differences in clinical profiles and multivariate regression to determine variables associated with subsets of loneliness. Results LLD patients reported more emotional loneliness but not social loneliness than healthy controls (p < 0.001). Emotional loneliness was the only significant predictor of suicidal ideation, particularly on patients with early-onset depression, explaining 26.8% of the effect (p < 0.001). Finally, the effect of medical comorbidity on depression severity was mediated by emotional loneliness(Z = 2.159, p = 0.031). Conclusion The current research highlights more attention should be placed on the age of onset and medical comorbidity in elderlies with depression. The distinction between emotional loneliness and social loneliness is better understood in the Asian population, reinforcing the importance of taking cultural influence into account when understanding psychological constructs.