Research on the etiology of psychiatric disorders have important implications for early detection of high-risk populations, development or implementation of possible preventive interventions, determination of current and future treatment modalities and prediction of treatment response and course of the illness. Bipolar disorder (BD) is a chronic and seriously debilitating illness. It has been known that, like most of other psychiatric disorders, genetic and neurobiological factors have important role in the etiology of BD. However despite family, twin, adoption, and molecular genetic studies have shown genetic vulnerability/ transmission of BD in adult population, the data regarding young population are limited and only in its early stage. Current literature shows that pediatric bipolar disorder (PBD) may differ from adult illness regarding a variety of factors such as clinical and phenomenological features, treatment response, and course of the illness. While a number of factors may be contributing to these differences (e.g., age and developmental level), it remains crucial but largely unknown how much of that has been contributed by the etiological factors. This article aims to present and discuss, in the light of current literature, genetic and neurobiological factors in the etiology of PBD. We performed a search on PubMed using different combinations of keywords "juvenile/ pediatric bipolar disorder", "bipolar disorder children/ adolescents", "etiology", "genetics", "brain imaging", "neurobilogical factors", and "family studies" and reviewed fulltext or abstracts of relevant articles. We also benefited from print books particularly the last (fourth) edition of Lewis' Textbook of Child and Adolescent Psychiatry.