Artificial fertilization is used for the stable production of domestic animals, conservation of rare animals, and infertility treatment. However, the success rate of artificial fertilization is limited; thus, a more effective approach is desired. Cattle workers in Japan often add licorice grass to the herbage given to their animals before performing artificial insemination in an effort to increase the pregnancy rate. To examine the effects of licorice on fertilization success in mice, an aqueous extract of licorice was added to the culture medium used for insemination. The results were compared to those using glycyrrhizin, a major active constituent of licorice. The fertilization rate was improved by the aqueous licorice extract, but not specifically by glycyrrhizin. Thus, flavonoids in licorice other than glycyrrhizin may improve the success rate of artificial fertilization.