This study reveals that the RNA N6-methyladenosine (m6A) demethylase SlALKBH2 undergoes a reduction–oxidation (redox) modification in which hydrogen peroxide mediates the oxidation and the reductase SlNTRC catalyses the reduction. This redox modification affects SlALKBH2 protein stability, thereby modulating its physiological function in the regulation of normal ripening of tomato fruits.