Background: A growing interest in long-term sequelae of COVID-19 has prompted several systematic literature reviews (SLRs) to evaluate long-COVID-19 effects. However, many of these reviews lack in-depth information on the timing, duration, and severity of these conditions. Objectives: Our aim was to synthesize both qualitative and quantitative evidence on prevalence and outcomes of long-term effect of COVID-19 through an umbrella review. Design: Umbrella review of relevant SLRs on long-COVID-19 in terms of prolonged symptoms and clinical conditions, and comprehensively synthesized the latest existing evidence. Data Sources and Methods: We systematically identified and appraised prior systematic reviews/meta-analyses using MEDLINE, Embase, and Cochrane database of systematic review from 2020 to 2021 following the preferred reporting items for systematic reviews and meta-analyses guidance. We summarized and categorized all relevant clinical symptoms and outcomes in adults with COVID-19 using the Medical Dictionary for Regulatory Activities System Organ Class (MedDRA SOC). Results: We identified 967 systematic reviews/meta-analyses; 36 were retained for final data extraction. The most prevalent SOC were social circumstances (40%), blood and lymphatic system disorders (39%), and metabolism and nutrition disorder (38%). The most frequently reported SOC outcomes within each MedDRA category were poor quality of life (59%), wheezing and dyspnea (19−49%), fatigue (30−64%), chest pain (16%), decreased or loss of appetite (14–17%), abdominal discomfort or digestive disorder (12−18%), arthralgia with or without myalgia (16–24%), paresthesia (27%) and hair loss (14–25%), and hearing loss or tinnitus (15%). Conclusion: This study confirmed a high prevalence of several long COVID-19 outcomes according to the MedDRA categories and indicated that the majority of evidence was rated as moderate to low. Registration: The review was registered at PROSPERO (https://www.crd.york.ac.uk/prospero/) (CRD42022303557).