The effect of skeletal muscle mass (SMM) on the outcomes of sorafenib treatment for hepatocellular carcinoma (HCC) has not been established. We measured the SMM in HCC patients treated with sorafenib, evaluated the patients’ survival, and evaluated the association between skeletal muscle depletion and sorafenib treatment. Of the 97 HCC patients treated with sorafenib at our institution in the period from July 2009 to February 2015, our study included 69 patients (51 males, 18 females) who had received sorafenib for ≥ 8 weeks and whose follow-up data were available. SMM was calculated from computed tomography images at the mid-L3 level (cm2) and normalized to height (m2) to yield the L3 skeletal muscle index (L3-SMI, cm2/m2). The median L3-SMI value was higher in the males (43 cm2/m2) compared to the females (36 cm2/m2). In the males only, the multivariate Cox regression identified an L3-SMI <43 cm2/m2 as independently associated with higher mortality compared to an L3-SMI ≥43 cm2/m2 (hazard ratio 2.315, 95% confidence interval: 1.125-4.765, p=0.023). Skeletal muscle depletion is a factor predicting poor prognosis for male patients with advanced HCC treated with sorafenib.