Abstract The present Letter introduces a novel approach to test the efficiency of spin crossover materials with regard to structural fatigability. By measuring single-crystal mosaicity, structural fatigability is evidenced in a gradual SCO iron compound. The non fatigability of the analogue non-SCO zinc compound demonstrates the role of SCO in such observation. The mosaicity strongly increases during the first cycles. It is therefore clearly shown that fatigability can affect non-cooperative SCO systems. Magnetic properties appear however not altered by the observed structural fatigability which is thus related to mechanical aspects of SCO.