Rapid synchronized seed germination is desirable to ensure seedling establishment and improve crop yield. However, abiotic stresses from drought, salinity, and heavy metals have a negative impact on seed germination. The application of silicon (Si) has emerged as a promising approach for improving seed germination, especially under unfavorable conditions. However, the mechanisms of Si action have not been systematically studied in germinating seeds under conditions of abiotic stress. Considering the potential importance of sustainable agriculture, here we review recent findings of how seeds of numerous species, including several important crops, respond to Si treatment under abiotic stress. Exogenous Si has multiple effects on embryo viability, reserve mobilization, hormone/enzyme activity, membrane integrity, antioxidant metabolism, and regulation of gene expression in seed germination.