Objective:Loneliness and social isolation have negative health consequences and are associated with depression. Personality characteristics are important when studying persons at risk for loneliness and social isolation. The objective of this study was to clarify the association between personality factors, loneliness and social network, taking into account diagnosis of depression, partner status and gender.Design:Cross-sectional data of an ongoing prospective cohort study, the Netherlands Study of Depression in Older Persons (NESDO), were used.Setting and participants:474 participants were recruited from mental health care institutions and general practitioners in five different regions in the Netherlands.Measurements:NEO-Five Factor Inventory (NEO-FFI) personality factors and loneliness and social network were measured as well as possible confounders. Multinominal logistic regression analyses were performed to analyse the associations between NEO-FFI factors and loneliness and social network. Interaction terms were investigated for depression, partner status and gender.Results:Higher neuroticism and lower extraversion in women and lower agreeableness in both men and women were associated with loneliness but not with social network size irrespective of the presence of depression. In the non-depressed group only, lower openness was associated with loneliness. Interaction terms with partner status were not significant.Conclusions:Personality factors are associated with loneliness especially in women. In men lower agreeableness contributes to higher loneliness. In non-depressed men and women, lower openness is associated with loneliness. Personality factors are not associated with social network size.