This manuscript explores the possibilities and challenges of art–science integration in facilitating collaborative sustainability action in local settings. To date, much sustainability education is prescriptive, rather than participatory, and most integrated art–science programming aims for content learning, rather than societal change. What this means is that learners are more often taught “what is” than invited to imagine “what if?” In order to envision and enact sustainable alternatives, there is a need for methods that allow community members, especially young people, to critically engage with the present, imagine a better future, and collaboratively act for sustainability today. This manuscript introduces a methodological framework that integrates the arts and sciences to facilitate: (1) transdisciplinary learning, focusing on local sustainability challenges; (2) participatory process, bringing experience-based knowledge into conversation with research-based knowledge; and (3) collaborative sustainability action, inviting community members to envision and enact sustainable alternatives where they live. The transformative potential of this framework is examined through international case studies from countries representing the richest and poorest in the Western hemisphere: a multi-site research study and after-school program for climate change education and action in collaboration with children in the Western US; and a multi-cycle research study and community arts center course for environmental photography and youth-led water advocacy in Southern Haiti. Despite many shared characteristics, case studies diverge in important ways relative to the sustainability challenges they sought to address, the specific context in which activities took place, and the manner in which art–science integration was practiced. Across cases, however, art–science integration facilitated participants’ learning, connection, and action for sustainability. Framed by the shared aims of transdisciplinary approaches, this manuscript discusses methodological hurdles and practical lessons learned in art–science integration across settings as well as the transformative capacity of alternative pedagogical and research practices in building a sustainable future.