Delirium occurs in 50-80% of end-of-life patients but it is often misdiagnosed. Identification of clinical factors potentially associated with delirium onset can lead to a correct early diagnosis. To this aim, we conducted an observational prospective study on patients from an Italian Palliative Care Unit (PCU) in 2018-2019 and evaluated the presence of clinical factors at patients’ admission. We then compared their presence in patients who developed delirium and in those who did not during follow-up. On 503 enrolled patients, 95 (18.9%) developed delirium. In univariate analyses, factors significantly more frequent in patients with delirium were advanced age, care in hospice, very compromised performance status, hypoxia, high number of simultaneous clinical factors, presence of breathlessness, poor well-being, severe drowsiness, and background therapy with haloperidol and drugs acting on CNS. In multivariate analyses, setting of care (odds ratio, OR, 1.68 for hospice versus home care, 95% confidence interval, CI 1.02-2.75; p=0.040), and administration of psychiatric drugs (OR 1.74 for administration versus no administration, 95% CI 1.08-2.81; p=0.023) were significantly associated with the risk of developing delirium, while the associations with age (OR 1.82 for > 80 years versus ≤ 70 years, 95% CI=0.98-3.36; p=0.046) and presence of breathlessness (OR 1.70, 95%, CI 0.99-2.89, p=0.053) were of borderline significance. The study indicates that some clinical factors are associated with the probability of delirium onset. Their evaluation in PC patients could help the healthcare professionals to timely identify the development of delirium in those patients.