Loneliness is a risk factor for morbidity as well as mortality. Older people are more vulnerable to feeling alone due to age-associated changes and losses they might experience. This study aimed to analyze sociodemographic, psychosocial, and mental health variables related to loneliness in the elderly. A random sample of 419 people over 65 years old from the Community of Madrid was used. The UCLA Loneliness Scale, the CIDI65+ Diagnostic Interview, and the WHOQOL-BREF Quality of Life Measure were administered. A regression p model was estimated to identify the variables that best predict loneliness associated with old age. Loneliness-associated variables included living alone t(161.41) = 2.07; p < .040, marital status F(5, 404) = 4.52; p < .001, frequency of economic problems F(1, 408 ) = 4.86; p < .028, quality of life F(4, 405) = 7.36; p < .001, satisfaction with life F(4, 405) = 3.80; p < .005, satisfaction with social relationships F(4, 405) = 19.50; p < .001, presence of a mental disorder (t(98.70) = 2.92; p < .004), and having an anxiety disorder (t(51.11) = 2.19; p < .033). The results presented in this paper highlight some predictors of loneliness in older people that could be useful in intervention, to minimize harmful conditions that can lead to loneliness in people over 65.