Ambulatory electrocardiogram (ECG) monitoring frequently identifies incidental arrhythmias, but their prevalence in community-based atrial fibrillation (AF) screening remains uncertain. For this systematic review, we searched PubMed, Embase, Cochrane, and CINAHL through January 2025 for studies on ECG abnormalities in community-based screening. Eligible studies included randomized trials or observational cohorts without prior AF that used ≥24-hour continuous rhythm monitoring and reported at least 1 incidental non-AF finding. We included 25 publications (17 cohorts, 136,344 participants; mean age 41-80 years, 0%-100% female). Non-AF abnormalities occurred in 4%-96%, including supraventricular and ventricular arrhythmias and conduction defects. Meta-analyses demonstrated substantial heterogeneity in the reported prevalences of most potentially serious incidental findings, and other non-AF abnormalities. Sustained ventricular tachycardias were the only exception, showing low heterogeneity (I2 = 0.00%) and low pooled prevalence (0.2%). Overall, the prevalence of non-AF incidental findings during continuous ambulatory ECG screening in AF-free primary care and community-based cohorts varied widely, largely reflecting differences in definitions and reporting practices. This highlights the need for uniform reporting and further research into the prevalence and clinical relevance of these findings.