The governance of several cross-cutting challenges, such as food security, climate change, and sustainable development, calls for integrative policy approaches. However, efforts to better theorize the drivers of integration beyond listing explanatory factors remain weak. Viewing integration as a process of policy change for dealing with complex problems, this study argues that policy integration analysis can benefit from an advocacy coalition approach (ACF) to address this theoretical gap. It illustrates the analytical framework by empirically investigating the drivers of policy (dis)integration in Brazil's subnational water policy introduced in the 2010s. The level of conflict between coalitions, adjustment of policy beliefs, coordination within and across coalitions, and existence of venues for interaction and policy-oriented learning were presented as factors that can foster or hinder the integration of public policies. Moreover, the study discusses the potential to acknowledge in ACF the mechanisms for coordinating policy actors and instruments, which would facilitate the analysis of the policy processes of cooperation. It also demonstrates that recent droughts in Northeast Brazil have been increasingly related to the local impacts of climate change, contributing to reframing water management as a cross-sectoral climate and water governance issue. The analysis was based on a literature review, semi-structured interviews, and social network analysis.