Helping behaviour is an intentional act to benefit others. Due to constant, overwhelming distractions available massively in urban settings or urban-overload hypothesis, numerous research have unfortunately shown that people in the cities are less and less likely to engage in helping behavior. Hence, it is important to promote helping behaviour, particularly in female adolescents as they start to develop their social roles as the nurturing gender. Helping behaviour is influenced by a number of environmental and individual factors. One of those factors is bystander effect -how the presence of others around the event of emergency influences the decision to help. This between-subject experiment aims to find out the influence of bystander effect on helping behaviour of sixty 15-18 years-old female high school students purposively sampled for this research. Observational data of randomized control and experiment groups show significant influence of bystander effect on participants' helping behaviour toward a research confederate acting to be in need of assistance (independent t-test score: 3.29, with 0.05 level of significance, 58 degree of freedom, 1.671 critical values). This concludes the influence of bystander effect on helping behaviour of female adolescents.