Transitions in nutrition patterns tend to emerge through industrialization and economic development. We hypothesized that the dietary patterns among South Korean adults who were 20 years or older have changed significantly from 1998 to 2010. Herein, a repeated cross-sectional analysis of data was followed for 140601 adults. We noted changes in consumption, after adjusting for age, sex, body mass index, and exercise, and tested the trends across the study period. Factor and cluster analyses were used to derive dietary patterns. A decrease in traditional Korean food consumption, including cereals, vegetables (252-176 g), and Kimchi (127-82 g), occurred, whereas fruit (172-252 g), egg, and fried food intakes increased (P < .05). Total daily energy intake declined steadily from 1931 in 1998 to 1691 kcal in 2010. Carbohydrate intakes were unchanged over the study period; however, fat-derived energy intake increased slightly from 19.7% to 20.0% (P < .05). Our factor and cluster analyses identified 3 dietary patterns: "Korean" diet (rice, vegetables, and Kimchi), "Western" diet (soda, eggs, and oil), and "New" diet (low sugar and high fruit and dairy product intakes). Compared to 1998, approximately 40% of participants still followed a Korean diet in 2010. Interestingly, the popularity of the Western diet fell by approximately 20%, whereas the new diet pattern increased 2-fold over the study period. Overall, these data show secular trends in dietary patterns that included a preservation of the traditional Korean diet and the emergence of a new diet pattern, and it demonstrated a unique transition in food and nutrient intakes in Korea.