XIAP, X-linked inhibitor of apoptosis protein, is a member of the inhibitor of apoptosis protein (IAP) family known for its important conserved inhibitory effect on caspase activity. Since the introduction of XIAP almost three decades ago, numerous experimental studies have been performed for a wide range of cellular pathways and mechanisms. In this perspective, we summarize key trends of XIAP as an important regulator of cellular signaling. Experimental research indicates that XIAP as a key molecule of cell death not only suppress caspases and apoptosis, but also regulates inflammatory signaling, mitogenic kinase signaling, cell proliferation as well as cell invasion and metastasis. In this review, we provide basic knowledge of the roles of XIAP, explain its role in necroptosis, anoikis, autophagy and neuronal differentiation. XIAP is involved in regulating intracellular ROS production and copper homeostasis which this review focuses on. A different face of XIAP in response to DNA damage and chronic ER stress is also discussed.