Introduction: Gastroenteritis is a major public health concern, particularly in low-income countries. Adenovirus types 40 and 41 are associated with diarrhoea in humans. Approximately 1.7 billion cases of diarrhoea occur each year, with over 525,000 deaths among young children globally. This study aims to determine the prevalence of adenoviruses and astroviruses in patients and marine animals in the Republic of Guinea. Methods: Biological samples were collected from three localities (Kindia, Gueckédou, and Conakry) and analysed using qPCR and RT-PCR. Results were examined based on the type of diarrhoea, age, gender, season, and socio-professional category. Statistical analysis was performed using the z-test to evaluate the significance of observed differences. Results: Positivity rates varied by location: Kindia showed the highest prevalence, particularly in liquid diarrhoea (7.41%). Adenoviruses were more frequent (33.23% of 250 samples), while astroviruses were detected in only 0.71% of cases. Adenovirus prevalence was higher during the rainy season and among children (8.19%), followed by young adults (5.26%). Differences based on gender and socio-professional categories were not statistically significant (p=0.52). One case of astrovirus (out of 40 samples) was detected in marine animals. Conclusion: The study highlights a significant circulation of adenoviruses, especially among children and during the rainy season. The results suggest that environmental and sanitary factors may influence transmission.