This paper aimed to clarify the association of mid-adolescent dietary practices and experiences with adult eating behavior and attitudes using individual data from the “Survey of Attitudes toward Shokuiku (food and nutrition education), 2019” put forth by the Ministry of Agriculture, Forestry and Fisheries of Japan. We applied conditional mixed-process models to estimate the parameters simultaneously, and used them to predict current eating consciousness, current eating behaviors in a balanced diet, dietary behavior, and attitudes toward preventing or improving lifestyle-related diseases as dependent variables. As a result, compared to those who did not have good dietary practices and experiences in mid-adolescence, participants who had good dietary practices and experiences in the same period displayed greater interest in practicing a healthier diet. These participants frequently consumed a combination of staple foods, main dishes, and side dishes, and were more concerned about preventing or improving lifestyle-related diseases. In conclusion, mid-adolescent dietary practices and experiences had a lasting influence on adult eating behaviors and attitudes in Japanese participants.