Adjacent inter-provincial cooperative governance is a government governance strategy to reduce local protection and market segmentation under the administrative division system, and to promote the cross-regional flow of production factors. It is also an inherent part of provincial open governance and integrated urban-rural development. However, subject to the administrative boundaries of local governments’ governance powers and performance assessment for a long time, as well as the increasingly solidified local interests in the competitive development game, adjacent inter-provincial cooperative governance has become a blind area of government governance or a selective autonomous behavior. In 2020, the state proposed to build a new development pattern, which aims to expand domestic demand, unblocking economic circulation, and building a unified national market. This policy provides a new opportunity for adjacent inter-provincial cooperative governance, and the exploration of specific path strategies has become an important issue under the construction of a new development pattern. Based on the theory of collaborative governance and the Chinese governance context, this paper constructs an analysis framework of consensus–organization–action for adjacent inter-provincial collaborative governance, selects Chongqing–Guizhou collaborative governance as a case, uses semi-structured interview method to collect data, and explores the path strategy of inter-provincial collaborative governance under the new development pattern. It is found that adjacent inter-provincial collaborative governance is a multi-dimensional systematic governance action process in which stakeholders of neighboring provinces (autonomous regions or municipalities) build a decentralized collaborative organization system based on and guided by collaborative consensus. Under the new development pattern, the path strategy of adjacent inter-provincial collaborative governance should first clarify the requirements of national strategic policies, the needs of inter-provincial cooperative development, the expectations of market players and the public, and gather the consensus of relevant stakeholders on collaborative governance. Second, connect national strategic policies and provincial governance plans, build a decentralized overall layout, and make a good first hand in the collaborative development of adjacent areas and self-organization. Third, give play to the relative advantages and complementary functions of horizontal coordination, longitudinal management, and network governance, hold the cattle nose project, and focus on improving mechanisms for opening up and cooperation as well as joint ecological protection and governance, promote the integration of infrastructure and basic public services, promote the integration and upgrading of industrial chains, and prevent urban and rural poverty return and promote integrated development. Such a path strategy provides a systematic innovation blueprint and action plan for adjacent inter-provincial cooperative governance in the new development pattern, helps to improve the efficiency and sustainability of inter-provincial cooperative governance under the administrative division system, and can also promote the construction of a unified national market and coordinated regional development in the open governance of provinces.