Across the United States, approximately 180 million people rely on drinking water supplies that originate in forested watersheds. When wildfires burn these source watersheds, impacts can be complex, unpredictable, expensive, long-lasting, and far-reaching; affecting downstream water utilities, public health, aquatic ecosystems, and communities while testing their resilience. Because these consequences span ecological, biogeochemical, engineering, and social systems, providing solutions to wildfire threats to water security cannot be achieved by a single discipline or organization. The Wildfire and Water Security (WWS) Project is an interdisciplinary, multi-institutional effort focused on co-producing actionable science to support forest and drinking water managers. The project brings together 65+ members from 13 organizations, including universities, federal agencies, and a non-profit organization, as well as more than 25 external partners and collaborators. Our shared vision is to ensure forest and drinking water managers have enhanced information and tools to safeguard water supplies and reliably deliver clean drinking water to communities from forested watersheds that have been impacted by wildfire. To support this vision, WWS is organized into five research focus areas: source water quality, watershed and ecological processes, drinking water treatment, human dimensions, and integration. Here we share stories and lessons learned from across the project that illustrate both the successes and challenges of coordinating science across disciplines, institutions, and career stages. We also highlight experiences with external partner and science user engagement, internal and external communication strategies, data management, and project leadership. We reflect on early challenges associated with transdisciplinary science, including rapid funding timelines that limited initial team science planning, time commitments required to create shared understanding of cross-disciplinary consideration, and a willingness and vulnerability to step outside familiar disciplinary silos. These same challenges also revealed effective strategies such as in-person all-hands meetings, informal spaces for cross-team communication, and embracing play and fun in the scientific process. Together, these approaches have supported meaningful progress in addressing the interdisciplinary problem of wildfire impacts on water. By sharing these successes and challenges, we aim to provide practical insights, while continuing to learn from others, about collaborative, co-produced science that can be translated into decision-relevant outcomes.