The transcription factor NF-κB is crucial for numerous cellular functions such as survival, differentiation, immunity, and inflammation. A key function of this family of transcription factors is regulation of osteoclast differentiation and function, which in turn controls skeletal homeostasis. The IκB kinase (IKK) complex, which contains IKKα, IKKβ, and IKKγ, is required for activation of NF-κB, and deletion of either IKKα or IKKβ resulted with defective osteoclast differentiation and survival. We have recently investigated the details of the mechanisms governing the role of IKKβ in osteoclastogenesis and found that constitutively active IKKβ in which serine residues 177/181 were mutated into negatively charged glutamic acids instigates spontaneous bona fide receptor activator of NF-κB ligand (RANKL)-independent osteoclastogenesis. To better understand and define the functional role of IKKβ domains capable of regulating the osteoclastogenic activity of IKK, we investigated key motifs in the activation T loop of IKKβ, which are potentially capable of modulating its osteoclastogenic activity. We discovered that dual serine (traditional serine residues 177/181) and tyrosine (188/199) phosphorylation events are crucial for IKKβ activation. Mutation of the latter tyrosine residues blunted the NF-κB activity of wild type and constitutively active IKKβ, and tyrosine 188/199-deficient IKKβ inhibited osteoclastogenesis. Thus, tyrosines 188/199 are a novel target for regulating IKKβ activity, at least in osteoclasts.