Electronic government has proven a watershed in the domain of public administration, despite being difficult to pin down precisely. Indeed, the government-to-government (G2G) arena is one of the least studied aspects of this newly established field of knowledge, despite its importance in fostering cooperation and collaboration between government agencies, mainly with respect to the management of their knowledge, in order to increase the effectiveness of public administration. The main scope of this article is to present some key success factors for building G2G enterprises successfully. It also aims to show how public agencies themselves can benefit when they are electronically linked to others, thereby innovating and streamlining their working processes, in order to achieve greater agility and efficacy at reduced cost. In order to pinpoint the key G2G success factors, a single explanatory and successful case study approach was used, namely one involving the Brazilian Central Bank (BCB) and the Brazilian Justice Department (BJD). The BacenJud system developed by the Brazilian Central Bank was analyzed in a more detailed manner. This case—considered a success—shows how this G2G project made it possible for both the Brazilian Central Bank and the Brazilian Justice Department to achieve greater agility and effectiveness regarding the processing of legal demands made by the Brazilian Justice Department, thereby handing down its sentences at reduced cost. Furthermore, this study examined the factors that had a clear nationwide impact on the success of this endeavor in the realm of the Justice Department. Therefore, this article intends to answer the following research question: From the case study analyzed, what are the key success factors in the implementation of government-to-government processes between public agencies in Brazil?