This study aimed to identify the influence factors for snacking-avoidance behavior among elementary schoolchildren. We recruited 940 Taipei schoolchildren and used five validated questionnaires to assess family affluence, snacking nutrition knowledge, attitude, and motivation to avoid unhealthy snacks. Social support from parents and peers for refusing unhealthy snacks, and adolescents’ willingness to comply were also examined. Motivation to avoid unhealthy snacks or drinks was enhanced when support was given by parents, teachers, and peers. Participants who reported higher levels of social support were more likely to have a positive attitude towards healthy snacking and were more motivated to avoid unhealthy snack options. In conclusion, social support from significant others, attitudes, and nutrition knowledge all help schoolchildren to avoid unhealthy snacks.