To define the risk factors and clinical outcomes of community-onset bacteremia caused by extended-spectrum β-lactamase (ESBL)-producing Escherichia coli (ESBLEC), we analyzed 50 consecutive cases of community-onset bacteremia caused by ESBLEC at a secondary hospital in South Korea from 2005 to 2010. Risk factors were assessed by conducting a case-double control study in which cases were compared with (1) control patients with community-onset bacteremia due to non-ESBLEC, and (2) those with community-onset bacteremia not caused by E. coli. Clinical outcome was assessed among patients with community-onset E. coli bacteremia. Community-onset bacteremia due to ESBLEC accounted for 6.7% of all community-onset E. coli bacteremia. In addition, an increasing proportion of ESBLEC among patients without any healthcare risk factors was observed. Comparison with both control groups revealed that the recent use of antibiotics (odds ratio [OR], 4.3; 95% confidence interval [CI], 1.5-12.3) was an independent risk factor for ESBL acquisition. Factors influencing the 30-day mortality were a high Acute Physiology and Chronic Health Evaluation (APACHE) II score (OR, 1.5; 95% CI, 1.1-2.0) and severe sepsis or septic shock (OR, 26.6; 95% CI, 1.5-470.7) and malignancy (OR, 11.9; 95% CI, 1.1-134.8). Increased mortality was not statistically associated either with ESBL production or with inappropriate empirical therapy. ESBLEC has emerged as a significant cause of community-onset bacteremia in this hospital, suggesting that ESBLEC are widely disseminated in the South Korean community.