The maintenance and repair of adult skeletal muscle rely on molecular and cellular mechanisms that sustain tissue homeostasis during regeneration of injured myofibers. The NF-κB pathway has emerged as a critically important signaling network in skeletal muscle. Depending on the type of stimulus, activation of NF-κB signaling can occur through the classical or alternative pathway. In skeletal muscle, the classical pathway promotes myoblast proliferation and inhibits differentiation. In contrast, alternative NF-κB signaling is activated upon myoblast differentiation and required for myoblast fusion and promoting an oxidative metabolic phenotype. Furthermore, pathological NF-κB activation occurs in several muscle diseases, including Duchenne muscular dystrophy (DMD). TNF-like weak inducer of apoptosis (TWEAK) is a membrane bound and soluble cytokine that signals through Fn14, a highly inducible cell-surface receptor that is upstream of numerous signaling pathways including NF-κB. Upregulation of TWEAK/Fn14 signaling is seen in several chronic atrophic muscle disorders. In contrast, TWEAK/Fn14 signaling has also been suggested to play a beneficial role during muscle regeneration by promoting myoblast proliferation and fusion. In the present study, we examined the physiological role of TWEAK during skeletal muscle regeneration. Here, we demonstrate that TWEAK promotes secondary fusion (myoblast to nascent myotube fusion) through stimulation of NF-κB and upregulation of Myomixer mRNA. Specifically, we find that TWEAK is transiently expressed during fusion and the addition of TWEAK to nascent myotubes increases myoblast fusion. In vivo, TWEAK treatment of regenerating muscle enhanced myoblast fusion and increased muscle fiber cross-sectional area; whereas depletion of TWEAK inhibited fusion. Overall, our study demonstrates that TWEAK is required and beneficial for myoblast-to-myotube fusion and may be a potential approach to improve muscle regeneration in degenerative disorders such as DMD.