This study aimed to evaluate the effects of marjoram extract on oocyte maturation and gene expression in sheep oocytes and embryos. The first experiment studied the effect of the extract as an antioxidant to improve the in vitro maturation media used for sheep oocytes; the oocytes were matured in a TCM199 medium supplemented with 1 or 10 µg/mL of marjoram extract or the control, 0 µg, for 24 hr. Then, the maturation was estimated, and the gene expression was measured by using qPCR. The second experiment studied the effect of the extract on the development of sheep embryos produced in vitro; the fertilized oocytes were cultured in a SOF medium supplemented with 1 or 10 µg/mL of marjoram extract or the control, 0 µg, for 7 days. Then, the gene expression was measured using qPCR. The results showed that the marjoram extract did not improve nuclear maturation or the blastocyst rate. There was a significant increase in the level of GDF-9 gene expression in mature oocytes in the treatment groups. An increase in the expression of BCL-2 and EGR-1 genes was observed for the blastocysts in the 10 µg/mL group. We concluded that the marjoram extract did not improve nuclear maturation, but it did affect the expression of some genes in sheep oocytes and embryos.