Introduction The most typical presentation of COVID-19 is an acute respiratory syndrome whose most common symptoms include fever, cough, and dyspnea. However, gastrointestinal symptoms, such as diarrhea and nausea/vomiting, are increasingly reported in patients affected by COVID-19. This study aimed to describe the prevalence and time of onset of gastrointestinal symptoms in patients affected by COVID-19 and to find potential associations between gastrointestinal symptoms and clinical outcomes. Methods We performed a prospective single-center cohort study, enrolling patients who received diagnosis of COVID-19 at our institution between March 23, 2020, and April 5, 2020. We collected patient demographics and medical history, laboratory data, and clinical outcomes. Furthermore, we used a specifically designed questionnaire, administered to patients at time of diagnosis, to obtain data on the presence and time of onset of fever, typical respiratory symptoms, gastrointestinal symptoms, and other symptoms (fatigue, headache, myalgia/arthralgia, anosmia, ageusia/dysgeusia, sore throat, and ocular symptoms). Results In our cohort, 138 (69%) of 190 patients showed at least 1 gastrointestinal symptom at diagnosis; if excluding hyporexia/anorexia, 93 patients (48.9%) showed at least 1 gastrointestinal symptom. Gastrointestinal symptoms, in particular diarrhea, were associated with a lower mortality. At multivariate analysis, diarrhea was confirmed as independent predictive factor of lower mortality. Discussion Gastrointestinal symptoms are very frequent in patients with COVID-19 and may be associated with a better prognosis. These data suggest that, in some patients, the gastrointestinal tract may be more involved than the respiratory system in severe acute respiratory syndrome coronavirus 2 infection, and this could account for the less severe course of disease.