Mimivirus 1.2Mb genome is organized into a 30 nm nucleocapsid-like structure made of two closely related GMC-oxidoreductases, also composing the fibrils decorating its virions. In this work, we used MS-proteomics to characterize the protein content of virions and fibrils from different members of the Mimiviridae family (clade A: Mimivirus reunion -Mr- and Mimivirus M4 -M4, clade B: Moumouvirus australiensis -Ma- and Moumouvirus maliensis -Mm, clade C: Megavirus chilensis -Mc- and Megavirus vitis -Mv). Furthermore, we analyzed fractions purified from Mr mutants devoid of one of the two GMC-oxidoreductases (Mr_KOqu_143 and Mr_KOqu_946), or of both GMC-oxidoreductases (Mr_2KO) with or without expression of the GFP fused to the N-terminus of one GMC-oxidoreductase (Mr_2KO-GFP). Our results show the versatility of the protein content of the fibrils, with fibrils composed of different proteins inter- and even intra-clade, clades B and C viruses presenting fibrils with a protein composition closer to each other than that of clade A viruses.