Objectives: This study aimed to assess the adherence to dietary guidelines among college students in the post-COVID-19 era and examine the changes in their dietary habits as the learning environment transitioned from remote to in-person classes. Methods: We conducted a survey involving 327 college students in Daejeon from March to April 2023. The survey questionnaires included various factors, including age, gender, type of residence, frequency of use of delivery food, convenience food, and eating out. In addition, we investigated the extent of adherence to the dietary guidelines for Koreans and the degree of dietary changes following the post-COVID-19 shift in class format were investigated. For comparative analysis of the level of adherence to dietary guidelines in relation to dietary habit changes, an ANOVA and a post hoc Scheffe test were employed. We also performed a multiple linear regression analysis to identify dietary factors influencing the level of adherence to dietary guidelines. Results: The study revealed a high rate of convenience food consumption and a low rate of homemade food intake among students. There was a marked increase in the consumption of processed foods, convenience foods, dining out, sweet foods, high-fat fried foods, beverages, and alcohol following the transition from online to in-person classes. When examining adherence to Korean dietary guidelines, the highest scored practice was 'Hydration', and the lowest was 'Breakfast habit'. Increased consumption of convenience foods, late-night snacks, and dining out were negatively correlated with adherence levels to dietary guidelines, specifically correlating with 'Healthy weight', 'Hydration', 'Breakfast habit', and the total score of adherence. The adoption of 'regular meals' was positively associated with increased adherence levels to dietary guidelines. Conclusions: The transition from remote to in-person classes post-COVID-19 led to increased intake of convenience foods, dining out, sweet foods, high-fat fried foods, and alcohol. The rise in convenience food and late-night snack consumption negatively influenced several aspects of the dietary guidelines adherence, thereby suggesting the need for strategies to encourage healthy dietary habits among college students.