Introduction: In recent decades, the impact of insomnia on patients’ physical and mental health has increasingly become a subject of research. It is now a consensus that sleep disorders negatively affect quality of life, mood and cognitive function and are associated with an increased risk of physical diseases or worsen the prognosis of diseases that have already manifested. The aim of the study was to explore insomnia and associated factors in hospitalized patients with cardiovascular diseases. Material and method: In the present cross-sectional study, were enrolled 140 hospitalized patients with cardiovascular system in a public hospital in Attica prefecture, during the period 2024-2025. Participants were selected using the convenience sampling method. The measurement tool was “Athens Insomnia Scale (AIS)”, which included patients’ characteristics. Results: Of the 140 participants, 60.7% were male, 66.4% were over 70 years old, 69.6% were retired and 91.4% had a comorbidity. Regarding insomnia, at least 50% had AIS score less than 6 (median). In addition, 25% of patients had AIS score 10 (IQR). These values in relation to the possible range of values (0-24) of AIS scale indicate moderate levels of insomnia. Insomnia in patients was found to be statistically significantly related to occupation (p=0.003), disease of cardiovascular system (p=0.003), the years since diagnosis of the disease (p=0.030) and the existence of co-morbidity (p=0.013). Conclusions: Demographic and clinical characteristics are associated with insomnia in hospitalized patients with cardiovascular diseases.