Background Some patients experience long-term symptoms after COVID-19, but data on outpatients with mild-to-moderate COVID-19 are scarce. Objective To describe persisting symptoms more than 3 months after infection in PCR-confirmed COVID-19 in comparison to negative SARS-CoV-2 PCR outpatients and to identify predictors of long-term symptoms in COVID-19. Setting Outpatient clinics of a Swiss university center. Patients 418 symptomatic outpatients with PCR-confirmed COVID-19 (COVID-positive) and 89 negative SARS-CoV-2 PCR (COVID-negative). Design Prospective cohort study. Measurements Predefined long-term symptoms were evaluated though a phone interview >3 to 10 months after diagnosis. Associations between long-term symptoms and PCR test result, as well predictors of persisting symptoms in COVID-positive were evaluated by multivariate logistic regression including potential confounders (age, sex, smoking, comorbidities, time of the phone survey). Results The study population consisted mostly of young (median of 41 versus 36 years in COVID-positive and COVID-negative, respectively; p=0.020) health care workers (67% versus 82%; p=0.006).. Persisting symptoms were reported by 223 (53%) COVID-positive and 33 (37%) COVID-negative (p=0.006). Overall, 21% COVID-positive and 15% COVID-negative (p=0.182) consulted a doctor for these symptoms. Four surveyed symptoms were independently associated with COVID-19: fatigue (adjusted odds ratio [aOR] 2.14, 95%CI 1.04-4.41), smell/taste disorder (26.5, 3.46-202), dyspnea (2.81, 1.10-7.16) and memory impairment (5.71, 1.53-21.3). Among COVID-positive, female gender (aOR 1.67, 95% CI 1.09-2.56) and overweight/obesity (1.67, 1.10-2.56) were predictors of persisting symptoms. Limitations Undiagnosed SARS-CoV-2 infection in COVID-negative cannot be completely excluded. Conclusion More than half of COVID-positive outpatients report persisting symptoms up to 10 months after infection and 21% seek medical care for this reason. These data suggest that post-COVID syndrome places a significant burden on society and especially healthcare systems.