Ubiquitin is relatively modest in size but involves almost entire cellular signaling pathways. The primary role of ubiquitin is maintaining cellular protein homeostasis. Ubiquitination regulates the fate of target protein through the proteasome or autophagy-mediated degradation of ubiquitinated substrates. These substrates can be either intracellular or foreign proteins from invading pathogens. Legionella, a gram-negative intracellular pathogen, hinders the host-ubiquitin system by translocating dozens of effector proteins into the host cytosol. This review describes the current understanding of ubiquitin machinery from Legionella. We summarize structural and biochemical differences between the host-ubiquitin system and ubiquitin-related effectors of Legionella. Some of these effectors act almost similar to canonical host-ubiquitin machinery, while others have distinctive structures and perform noncanonical ubiquitination through novel biochemical mechanisms.