The objective of this study was to investigate bed collapse and expansion characteristics of different types of multi-walled carbon nanotubes (MWCNTs) in fluidized bed with a 0.14 m-ID x 2.4 m-height Plexiglas column. Three types of MWCNTs were used as bed materials: (i) N, NC7000 (TM) prepared by Nanocyl (R), (ii) S-f, fine entangled MWCNTs agglomerated by strong cohesive force such as van der Waals force, (iii) S-c, coarse entangled MWCNTs with a single particle. Similarity between MWCNTs and Geldart group particles was investigated based on bed collapsing process. Results showed that bed collapsing processes of N, S-f, and S-c were similar to those of Geldart groups A, C, and B particles, respectively. Based on bed collapse and expansion characteristics, dense phase voidages of N and S-f were 0.795 and 0.921, respectively, in bubbling fluidization at superficial gas velocity of 0.19 m/s. (C) 2018 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.