Authentic project-based learning (APBL) is a highly effective way for instructors to help students learn disciplinary skills, modes of thinking, and collaborative practices by creating solutions to real-world problems for real users and clients. While educational technology innovations can bolster APBL by making a promising but challenging pedagogy more effective, as with many areas of education instructor adoption is slow. Diffusion of innovations theory predicts that instructors will adopt and maintain their use of innovations if innovations are perceived to, and then do, address their challenges. To guide design of future APBL technologies, we interviewed 47 university APBL instructors about their most significant challenges and inductively analyzed the resulting interview transcripts. APBL instructors reported interrelated challenges of: (a) "scoping," sourcing challenges and balancing the needs of the program, students, and clients; (b) "curriculum" preparation, making the curriculum flexible enough for shifting project problems and codify standards to help students understand how to do quality work; (c) providing "assistance" to teams, including monitoring, and delivering assistance; and (d) "coordinating" a range of stakeholders involved in assisting teams, including co-instructors, clients, and students. To support instructor adoption in APBL, educational technology innovators might communicate existing technology, or create technological innovations, that provide: (a) scoping tools for sourcing projects, and forming teams; (b) authoring tools for sharing and remixing of curricular materials; (c) project management tools for team management and monitoring; and (d) coordination software to manage all APBL stakeholders.