Fast food is popular among children and adolescents; however, its consumption has often been associated with negative impacts on nutrition and health. This study examined current fast food consumption status among middle school students and explored factors influencing fast food consumption by applying Theory of Planned Behavior. A total of 354 (52.5% boys) students were recruited from a middle school. The subjects completed a pre-tested questionnaire. The average monthly frequency of fast food consumption was 4.05 (4.25 for boys, 3.83 for girls). As expected, fast food consumption was considered to be a special event rather than part of an everyday diet, closely associated with meeting friends or celebrating, most likely with friends, special days. The Theory of Planned Behavior effectively explained fast food consumption behaviors with relatively high $R^2$ around 0.6. Multiple regression analyses showed that fast food consumption behavior was significantly related to behavioral intention (b = 0.61, P < 0.001) and perceived behavioral control (b = 0.19, P < 0.001). Further analysis showed that behavioral intention was significantly related to subjective norm (b = 0.15, P < 0.01) and perceived behavioral control (b = 0.56, P < 0.001). Attitude toward fast food consumption was not significantly associated with behavioral intention. Therefore, effective nutrition education programs on fast food consumption should include components to change the subjective norms of fast food consumption, especially among peers, and perceived behavioral control. Further studies should examine effective ways of changing subjective norms and possible alternatives to fast food consumption for students to alter perceived behavioral control.