The deformation propagation and the formation ofcollapse bandsare investigated in a closed cell aluminiumfoam system by means of lab-basedexperiment, x-ray micro-tomography and the finite element modelling. We report mechanisms leading to the plastic strain localisation. We find that the local magnitude of the plastic strains inside the collapse bands are high compared to the applied bulk strain. The regions with large pores predominantly undergo collapse and subsequently, the structural heterogeneity slightly reduces.Additionally, we find that pores become increasingly connected due to the fracturing of cell walls.