Many genetic risk factors for major mental disorders have key roles in brain development. Thus, exploring the roles for these genetic factors for brain development at the molecular, cellular, and neuronal circuit level is crucial for discovering how genetic disturbances affect high brain functions, which ultimately lead to disease pathologies. However, it is a tremendously difficult task, given that most mental disorders have genetic complexities in which many genetic risk factors have multiple roles in different cell types and brain regions over a time-course dependent manner. Furthermore, some genetic risk factors are likely to act epistatically in common molecular pathways. For this reason, a technique for spatial and temporal manipulation of multiple genes is necessary for understanding how genetic disturbances contribute to disease etiology. Here, the authors will review the said technique, in utero electroporation, which investigates the molecular disease pathways in rodent models for major mental disorders. This technique is also useful to examine the effect of genetic risks at the behavioral level. Furthermore, the authors will discuss the recent progress of this technology, such as inducible and cell type-specific targeting, as well as nonepisomal genetic manipulation, which provide further availability of this technique for research on major mental disorders.