Few studies have examined overall patterns of eating alone in relation to the risk of metabolic syndrome (MetS) in Korean populations. The present study aimed to examine the relationship between patterns of eating alone and the risk of MetS in Korean adults. Data from the Korea National Health and Nutrition Examination Survey (KNHANES) for 2013–2015 were used, with 8988 Korean adult participants, including 3624 men and 5364 women, aged 18 to 64 years. Patterns of eating alone were categorized into eight groups based on the total frequency of eating alone on a daily basis in the past one year: (1) three times for breakfast, lunch, and dinner; (2) twice for breakfast and dinner; (3) twice for lunch and dinner; (4) twice for breakfast and lunch; (5) once for breakfast only; (6) once for lunch only; (7) once for dinner only; and (8) never eating alone. The presence of MetS has been defined by the National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III) and International Diabetes Federation (IDF). Multivariable logistic regression analyses were performed to assess the association between patterns of eating alone versus the risk of MetS after controlling for age, income, occupation, number of family members, generation types, marital status, smoking status, and physical activity. The prevalence of MetS was the highest in men and women aged 40–64 who had breakfast, lunch, and dinner alone (50.1% and 36.8%, respectively). Men who had dinner alone or lunch and dinner alone compared with those who eat with others had a significantly higher risk of MetS, with adjusted odds ratios (AOR) of 1.51, and a 95% confidence interval (CI) of 1.06–2.16; and an AOR of 1.54, with a 95% CI of 1.05–2.25, respectively. Women who had breakfast alone compared with those who ate with others had a significantly lower risk of MetS (AOR 0.70, 95% CI 0.53–0.94). In conclusion, patterns of eating alone are differentially associated with the risk of MetS in a representative sample of Korean adults. Future studies are warranted to identify dietary patterns across the different eating alone patterns in relation to various health outcomes in Korean adult populations.