INTRODUCTION: Since the beginning of the pandemic in early 2020, there have been numerous reports of symptoms that have lingered due to COVID-19. However, there is a lack of data concerning these persistent symptoms in non-hospitalized patients. This study sought to examine the prevalence of persistent symptoms at 18 months and beyond following the diagnosis of COVID-19 non-hospitalized patients. METHODS: A prospective cohort study comprised 212 non-hospitalized adult patients consecutively assessed from data available at tertiary care institutions through telephone interviews. During the interview, participants were routinely questioned about whether they were still experiencing any post-infection symptoms at the time of the study. RESULTS: Total 212 took part in the 18-month or longer follow-up survey. The most commonly reported symptoms during the acute phase were fever (n=149, 70.3%), weakness (n=118, 55.7%), and sore throat (n=100, 47.2%). At the 18-month and above follow-up, 167 patients (78.7%) reported at least one symptom continuing. The most common symptom at this time point was fatigue (n=109, 51.4%), followed by joint pain (n=57, 26.8%), and exertional dyspnea (24.5%). The possibility of symptoms returning after an 18-month follow-up and beyond was significantly lower in patients who had taken the COVID-19 vaccine (OR=0.29; 95% CI: 0.112-0.749; p=0.011) and those did not infect a second time (OR=0.232; 95% CI: 0.057-0.93; p=0.04). CONCLUSION: The present study reveals that clinical complications persist even at 18 months and beyond during follow-up, with a prevalence similar to earlier follow-up periods, regardless of the severity of the initial COVID-19 infection.