(1) Background: Loneliness, little studied in Nursing Homes (NHs), can affect physical and mental health. We aimed to verify the prevalence of loneliness in 5 NHs and its associated factors. (2) Methods: Cross-sectional study. Older adults aged 65 or over with preserved cognitive status were included. The De Jong Gierveld Loneliness Scale was used to assess overall, social, and emotional loneliness; sociodemographic and health-related variables were collected. The chi-square (or Fisher’s) test and logistic regression were used for bivariate and multivariate analysis respectively. (3) Results: The final sample consisted of 65 participants (81.5% female) with a mean age of 84±7.13. Prevalence of overall loneliness was 70.7% (95%CI:58.2-81.4), social loneliness 44.6% (95% CI: 33.1-56.6) and emotional loneliness 46.2% (95% CI: 34.5–58.1). Overall loneliness was associated with lower perceived quality of life (Odds Ratio-OR= 5.52, 95% CI:1.25-24.38) and NH with state subsidized places (OR=0.19, 95% CI: 0.05-0.74); social loneliness with having 0-1 children (OR=0.25, 95% CI: 0.08-0.77), and emotional loneliness with depression (OR=4.54, 95% CI: 1.28-16.08) and urinary incontinence (UI) (OR=4.65, 95% CI: 1.23-17.52). (4) Conclusions: Loneliness was present in almost 71% of residents and was associated with the type of NH and poorer quality of life, emotional loneliness with depression and UI and social loneliness with having less than 2 children.