Study objectives: Millions of COVID-19 survivors experience a wide range of long-term symptoms after acute infection, giving rise to serious public health concerns. To date, few risk factors for post-COVID-19 conditions have been determined. This study evaluated the role of pre-infection sleep quality/duration and insomnia severity in the incidence of long-term symptoms after COVID-19. Methods: This prospective study involved two assessments (April 2020 and 2022). At baseline, sleep quality/duration and insomnia symptoms in participants without current/prior SARS-CoV-2 infection were measured using the Pittsburgh Sleep Quality Index (PSQI) and the Insomnia Severity Index (ISI). At follow-up, we evaluated the presence of twenty-one symptoms (psychiatric, neurological, cognitive, bodily, and respiratory) one month (n=713, infection in April 2020-February 2022) and three months after COVID-19 (n=333, infection in April 2020-December 2021). Zero-inflated negative binomial models were used to estimate the effect of previous sleep on the number of long-term symptoms. Binomial logistic regressions were performed to evaluate the association between sleep outcomes and the incidence of each post-COVID-19 symptom. Results: Analyses highlighted a significant effect of pre-infection sleep on the number of symptoms one/three months after COVID-19. Previous higher PSQI and ISI scores, and shorter sleep duration significantly increased the risk of almost every long-term symptom at one/three months from COVID-19. Conclusion: This study suggested a prospective dose-dependent association between pre-infection sleep quality/quantity and insomnia severity with the manifestation of post-COVID-19 symptoms. Promoting sleep health may represent an effective preventive approach to mitigate the COVID-19 sequelae, with substantial public health and societal implications.