Muscle atrophy increases the production of reactive oxygen species and the expression of atrophy-related genes, which are involved in the ubiquitin-proteasome system. In the present study, we investigated the effects of β-carotene on oxidative stress (100 μM-H2O2)-induced muscle atrophy in murine C2C12 myotubes. β-Carotene (10 μM) restored the H2O2-induced decreased levels of myosin heavy chain and tropomyosin (P< 0·05, n 3) and decreased the H2O2-induced increased levels of ubiquitin conjugates. β-Carotene reduced the H2O2-induced increased expression levels of E3 ubiquitin ligases (Atrogin-1 and MuRF1) and deubiquitinating enzymes (USP14 and USP19) (P< 0·05, n 3) and attenuated the H2O2-induced nuclear localisation of FOXO3a. Furthermore, we determined the effects of β-carotene on denervation-induced muscle atrophy. Male ddY mice (8 weeks old, n 30) were divided into two groups and orally pre-administered micelle with or without β-carotene (0·5 mg once daily) for 2 weeks, followed by denervation in the right hindlimb. β-Carotene was further administered once daily until the end of the experiment. At day 3 after denervation, the ratio of soleus muscle mass in the denervated leg to that in the sham leg was significantly higher in β-carotene-administered mice than in control vehicle-administered ones (P< 0·05, n 5). In the denervated soleus muscle, β-carotene administration significantly decreased the expression levels of Atrogin-1, MuRF1, USP14 and USP19 (P< 0·05, n 5) and the levels of ubiquitin conjugates. These results indicate that β-carotene attenuates soleus muscle loss, perhaps by repressing the expressions of Atrogin-1, MuRF1, USP14 and USP19, at the early stage of soleus muscle atrophy.