Fermentation has attracted increasing attention in pig industry, because of low costs and numerous benefits on pig growth and health as well as environmental improvement, although the mechanisms remain largely unknown. In the present study, fermented corn-soybean meal significantly improved average daily gain and gain:food ratio (P < 0.05). Fermented feed (FF) significantly increased insulin-like growth factor 1 (IGF1) transcription in liver (P < 0.05). Meanwhile, fermented meal significantly enhanced the binding of CCAAT/enhancer-binding protein beta (C/EBPβ) to IGF1 promoter and C/EBPβ expression in liver (both P < 0.05). FF tended to increase IGF1 proteins in liver and serum too (both 0.05 < P < 0.10). Meanwhile, FF slightly but significantly increased hepatic and circulating triglyceride and total cholesterol levels, as well as serum ratio of high-density to low-density cholesterol (all P < 0.05). Our data indicated that FF could significantly augment the binding of C/EBPβ to IGF1 promoter and promote hepatic IGF1 expression and production, thus boost pig growth.