Background: Depression includes negative interpretations of events, dislike of the self, and negative appraisal of the future. Objectives: The present study was conducted to investigate the effect of educational programs of cognitive-behavior modification and feeding behavior on serotonin levels and depression symptoms in university students. Materials & Methods: This quasi-experimental study was conducted with a pretest-posttest and a control group design. The study population included all male and female bachelor degree students in the Faculty of Literature and Humanities of the University of Guilan, Guilan Province, Iran at the time of the research. Among 2854 students, using Morgan’s table, the sample size was determined as 340. In the following, 24 students with depression symptoms and other inclusion criteria were selected as the sample and randomly assigned to the experimental and control groups. During the twelve sessions of training, the number of participants decreased from 24 to 16. The study tools included the Beck depression inventory (1996), the food frequency questionnaire (2017), 21 food enjoyment questionnaire, and the blood test. The obtained data were analyzed by 1-way analysis of covariance in SPSS v. 24. Results: The analysis showed that the use of cognitive-behavior modification training reduced students’ depression (P<0.01). However, the use of feeding behavior training did not increase serotonin levels in students (P>0.05). Conclusion: Among people with depression symptoms, cognitive-behavior modification by focusing on their negative self-talk can be useful in creating sensible thoughts and positive inner dialogue. But in these people, feeding behavior training for two months did not change serotonin levels.