The use of the common marmoset monkey in biomedical research has increased recently, and further attention has been devoted to this model after the successful production of transgenic marmosets. To extend genetic engineering approaches to widespread biomedical research fields, efficient prolonged in vitro culturing of embryo development is necessary. We aimed to evaluate the effects of the size of the zona pellucida opening on promoting the hatching process in the marmoset embryo. Piezo-microdrilling of a 6-m opening in eight embryos resulted in four partially hatched embryos and one hatched embryo after 5 days of culture. Piezo-microdrilling a 20-m opening in 11 embryos resulted in nine partial hatchings and no hatched embryos. Piezo-scraping an 80-m opening in six embryos resulted in no partially hatched embryos and five hatched embryos. These results suggest that an 80-m opening, rather than 6-m or 20-m openings, is suitable to complete the hatching process in the marmoset embryo.