14-3-3 proteins are an acidic protein family that is highly conserved and widely distributed in eukaryotic cells. Recent studies have found that 14-3-3 proteins play critical roles in cell signal transductions, cell growth and differentiation, and protein synthesis. 14-3-3γ is an important member of 14-3-3 protein family. In our previous study, we found that 14-3-3γ was upregulated by estrogen in dairy cow mammary epithelial cell (DCMEC), but the function and mechanism of 14-3-3γ is not known. In this experiment, we first cultured and purified the primary DCMEC and found 14-3-3γ located both in the cytoplasm and nucleus by using immunofluorescence assay. Methionine, lysine, estrogen, and prolactin could upregulate the expression of 14-3-3γ, stimulate the secretion of β-casein and triglyceride, and raise the cell viability of DCMEC. We constructed a stable 14-3-3γ overexpression cell line of DCMEC and found that the expressions of mTOR and p-mTOR, the secretion of triglyceride and β-casein (CSN2), and the cell viability of DCMEC were all upregulated. We also observed the effects of 14-3-3γ gene silencing and gained consistent results with 14-3-3γ overexpression. These findings reveal that 14-3-3γ affects the mTOR pathway and regulates lactogenesis in DCMECs.