Obesity-induced inflammation is closely associated with the development of metabolic complications such as insulin resistance and type 2 diabetes. Several immune-signaling receptors and their counterpart ligands are known to be crucial for crosstalk between the adaptive and innate immune system, and they are implicated in various inflammatory pathologies. In this mini-review, I will discuss the involvement of the immune costimulatory molecule 4-1BB and its ligand in obesity-induced inflammation and metabolic complications.