Objectives: First, to seek if sociodemographic and health factors contribute differentially to the explanation of loneliness in institutionalized and noninstitutionalized older adults; and second, to analyze the influence of institutionalization on loneliness. Method: This work was based on two surveys of older adults aged 60 years or more in Spain. A group of 234 community-dwelling people and 234 nursing homes residents were selected ( n = 468). Logistic regression models were applied using the six-item De Jong Gierveld Loneliness Scale as dependent variable. Results: Depression was associated with loneliness in both populations. Sex and marital status contributed to explain loneliness among those living at home, whereas gathering with family, friends, and neighbors showed a significant effect in the institutionalized group. Institutionalization per se showed a strong effect on loneliness. Discussion: Findings have potential implications for targeting older adults at risk for loneliness.