Objectives: This study aimed to investigate the relationship between morningness, eating behaviors, positive and negative affect and eating chocolate and to evaluate these variables with regard to eating breakfast. Method: The study design was correlational. 125 undergraduate students of Faculty of Psychology and Education of University of Tehran completed Dutch Eating Behavior Questionnaire, Positive and Negative Affect Scale and Composite Scale of Morningness. 80 of these subjects then participated in a chocolate sham-palatability test. The number of chocolates participants tasted was considered as an objective measure of eating behavior. Results: Morningness had positive relationship with positive affect (r=0.35, p<0.01) but negative relationship with external eating (r=-0.24, p<0.01), though no relationship was found between morningness and negative affect. Among tested variables, only emotional eating was related to the number of chocolates in the test (r=0.25, p<0.01). Though the number of breakfast days per week was related to morningness (r=0.19, p<0.05), there was no difference between the study variables in participants who ate breakfast and those did not. Conclusion: The correlation between the number of chocolates consumed and emotional eating is an important finding of the study introducing the test for objective measurement of emotional eating phenomenon. In addition, morningness was correlated with positive affect and external eating that is in accordance to previous research.