Beyond geophysical challenges, climate change imposes unequal risks and burdens across affected groups and is unequally caused by them, exacerbating social injustices. Psychological measures to assess climate justice beliefs are missing. We therefore developed the Sensitivity to Climate Injustice (SCI) Scale to capture individuals’ evaluations of climate-related disparities between groups. Across four studies with German-speaking samples (N1 = 1,084; N2 = 1,998, N3 = 1,092; N4 = 1,119), the eight-item scale was validated, assessing two correlated factors: cause (perceived contribution disparities) and suffer (perceived burden disparities). The SCI showed mostly expected relations with other traits in a nomological network. Sensitivity to climate injustice also demonstrated strong criterion validity: the two factors differentially predict readiness for climate action and climate-relevant behaviour. By providing a theory-derived, reliable, and valid measure, the SCI fills a crucial gap, enabling psychological research on sensitivity to inequality as a potential driver of climate action.