It has been estimated that around one third of anthropogenic greenhouse gas (GHG) emissions originates from the way the humanity feeds itself. Current global production and consumption of animal protein account for a significant share of these emissions and associated long-term impacts on health, environment, and climate. While food insecurity persists globally, GHG emissions are likely to rise as more people gain access to adequate nutrition, including sufficient protein. In regions such as Europe, where protein intake is largely adequate and even exceeds recommendations, the majority still comes from animal-based sources (meat, dairy, fish, eggs) causing considerable climate impacts. The European Green Deal and Farm-to-Fork Strategy aim to reduce these impacts, in part by promoting substitution of some animal-based protein with alternative sources. While alternative proteins may play an important role in climate transition, it is not yet clear how their production systems are affected by climate change, to what extent they are able to adapt to these changes, or what their climate mitigation potential is. The paper presents a six-step methodology developed in the GIANT LEAPS Project to assess climate change adaptation and mitigation potential of alternative proteins and apply it to nine European produced sources shortlisted in the project (crickets, cultured meat, fava beans, lentils, microalgae, oats, quinoa, rapeseed, single-cell protein). The application of the methodology that contains climate vulnerability assessment combined with mitigation and adaptation options provides initial, comparable insights into climate vulnerabilities, adaptation capacities, and mitigation potentials of these novel protein production systems and highlights leverage points that can inform policy and investment in Europe's protein transition.