The Wnt/$eta$-catenin signaling pathway alters adipocyte differentiation by inhibiting adipogenic gene expression. $eta$-catenin plays a central role in the Wnt/$eta$-catenin signaling pathway. In this study, we revealed that tumour necrosis factor-$alpha$ (TNF-$alpha$), a potential negative regulator of adipocyte differentiation, inhibits porcine adipogenesis through activation of the Wnt/$eta$-catenin signaling pathway. Under the optimal concentration of TNF-$alpha$, the intracellular $eta$-catenin protein was stabilized. Thus, the intracellular lipid accumulation of porcine preadipocyte was suppressed and the expression of important adipocyte marker genes, including peroxisome proliferator-activated receptor-$gamma$ (PPAR$gamma$) and CCAAT/enhancer binding protein-$alpha$ (C/EBP$alpha$), were inhibited. However, a loss of $eta$-catenin in porcine preadipocytes enhanced the adipogenic differentiation and attenuated TNF-$alpha$ induced anti-adipogenesis. Taken together, this study indicated that TNF-$alpha$ inhibits adipogenesis through stabilization of $eta$-catenin protein in porcine preadipocytes.