Recent studies reported that the direct transformation of one differentiated somatic cell type into another is possible. In the present study, we were able to modulate the cell fate of somatic cells to take on male germ cell function by introducing cell extracts derived from porcine testis tissue. Fibroblasts were treated with streptolysin O, which reversibly permeabilises the plasma membrane, and incubated with testis extracts. Our results showed that the testis extracts (TE) could activate expression of male germ cell-specific genes, implying that TE can provide regulatory components required for altering the cell fate of fibroblasts. Male germ cell function was sustained for more than 10 days after the introduction of TE. In addition, a single TE-treated cell was injected directly into the cytoplasm of in vitro-matured porcine oocytes. The rate of blastocyst formation was significantly higher in the TE-treated nuclear donor cell group than in the control cell group. The expression level of Nanog, Sox9 and Eomes was drastically increased when altered cells were used as donor nuclei. Our results suggest that TE can be used to alter the cell fate of fibroblasts to express male germ cell function and improve the developmental efficiency of the nuclear transfer porcine embryos.