Co-production is an increasingly popular approach for environmental and sustainability research, but what is actually produced through its practice remains understudied. This paper reviews recent examples of co-produced research alongside current theorization on the topic. Focusing on the area of climate change adaptation, we find that co-produced climate change adaptation research appears to be improving knowledge use, among other positive outcomes, but a difference emerges between the range of outcomes reported in practice and the scope of ambition conceived through theory. This raises important questions about how the practice of knowledge co-production should be evaluated and, fundamentally, what we should expect to produce through co-production. We argue that understanding and reconciling the transformative potential of science-practice collaborations within the context of the incremental progress achieved through its current practice will catalyze a more integrated and actionable scholarship and practice.