The ubiquitin-proteasome system is a key proteolytic pathway activated during skeletal muscle atrophy. The proteasome however, cannot degrade intact myofibrils or actinomyosin complexes. In rodent models of diabetes mellitus and uraemia, caspase-3 is involved in actinomyosin cleavage, generating fragments that subsequently undergo ubiquitin-proteasome mediated degradation. Here, we demonstrate that caspase-3 also mediates denervation-induced muscle atrophy. Two weeks post tibial nerve transection the denervated gastrocnemius of caspase-3 knockout mice weighed more and demonstrated larger fibre-type specific cross sectional area than the denervated gastrocnemius of wild type mice. However, there was no difference between the caspase-3 knockout and wild type denervated muscles in the magnitude or pattern of actinomyosin degradation, as determined by Western blotting for actin and the 14kDa actin fragment. Similarly, there was no difference between the caspase-3 knockout and wild type denervated muscles in the magnitude of increase in proteasome activity, total protein ubiquitination, or atrogin-1 and MuRF1 transcript levels. In contrast, there was an increase in TUNEL positive nuclei in the denervated muscle of wild type compared to the caspase-3 knockout mice. Apoptotic signalling upstream of caspase-3 remained intact, with equivalent mitochondrial Bax translocation and cytochrome C release, and caspase-9 activation in the denervated gastrocnemius of wild type and caspase-3 knockout mice. In contrast, diminished PARP cleavage in the denervated muscle of caspase-3 knockout compared to wild type mice revealed apoptotic signalling downstream of caspase-3 was impaired, suggesting that the absence of caspase-3 protects against denervation-induced muscle atrophy by suppressing apoptosis as opposed to ubiquitin-proteasome mediated protein degradation.