In general, the rebound behavior of particles depends on the particle substrate material combination and the particle size. In the present investigation the rebound behavior of nanoparticle agglomerates is investigated in a low pressure impactor and compared to single spherical particles. For agglomerates, their structure and mechanical strength will also affect the rebound behavior. The rebound of openly structured agglomerates (fractal dimension D-f < 2) is determined by the primary particle size and the particle-substrate combination. The impact velocity required for rebound (critical velocity) is independent of the agglomerate size and equal to the critical velocity of single spherical particles having the same size as the primary particles. In case of agglomerate fragmentation no rebound was observed for openly structured agglomerates. For denser agglomerates (D-f > 2), the critical impact velocity decreases with increasing agglomerate size, where the decrease is more accentuated for higher fractal dimensions, finally approaching the behavior of spheres. (C) 2017 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.