BACKGROUND AND AIMS: Long COVID (LC) is a condition characterized by the persistence of physical or psychological symptoms after acute SARS-CoV-2 infection. While its pathophysiology remains unclear, it is essential to identify acute-phase risk factors associated with its development. This study aimed to investigate the association between symptoms during acute COVID-19 and the risk of developing LC, and to evaluate the impact of LC on functional status in a nonhospitalized population. METHODS: A retrospective observational case-control study was conducted between May 2022 and March 2024 including 434 participants with confirmed SARS-CoV-2 infection. Participants were classified as cases (those with LC;  = 226) or controls (those without LC;  = 208). Data were collected using a structured electronic form, including self-reported sociodemographic, clinical, and lifestyle information. Severity and number of acute symptoms were recorded. Functional status was assessed using the Post-COVID functional status (PCFS) Scale. Logistic and linear regression analyses were performed to explore associations, adjusted for potential confounders. RESULTS: Severe acute COVID-19 (defined as pneumonia or hospitalization) was associated with a significantly increased risk of LC (adjusted OR = 7.22; 95% CI: 2.79-18.70). Additionally, each additional symptom during the acute phase increased the odds of LC by 52% (adjusted OR = 1.52; 95% CI: 1.35-1.77). Dyspnea and chest pain were the symptoms most strongly associated with LC. CONCLUSION: The severity and symptom burden of acute COVID-19 are strongly associated with the development of LC and with long-term functional impairment. These findings highlight the importance of early identification and follow-up in patients with severe initial COVID-19 symptoms.