<p>Uniform seed germination and synchronized seedling establishment are essential for dahlia (<i>Dahlia variabilis</i>) breeding programs. This study examined the effects of ethephon, gibberellic acid (GA₃), and partial pericarp removal treatments on dahlia seed germination. The expression of ethylene biosynthesis genes, namely <i>DvACS</i> and <i>DvACO</i>, was also analyzed in seeds treated with ethephon and GA₃. Treatment of seeds with 1 mM ethephon for 1&#xa0;day markedly improved germination, and all seeds germinated within 3 days after sowing. In contrast, treatment of seeds with 2.88 mM GA₃ for 3 days resulted in 100% germination by 18 days after sowing, compared with 41.7% seed germination in the water control. Partial pericarp removal at the micropylar portion alone or at both the micropylar and chalazal portions increased germination frequencies to 73.3%, whereas nearly 50.0% of seeds with pericarp removal at the chalazal portion alone, as well as intact seeds, germinated by 25 days after sowing. The levels of expression of <i>DvACS</i> and <i>DvACO</i> were substantially increased in ethephon-treated seeds and gradually increased in GA₃-treated seeds, whereas minimal increases were observed in seeds of the water control. As levels of expression of <i>DvACS</i> and <i>DvACO</i> in ethephon- or GA₃-treated seeds were 2–4-fold higher than those in seeds of the water control, endogenous ethylene production induced by these phytohormones likely promotes dahlia seed germination. Thus, ethylene biosynthesis is positively regulated by ethephon and GA₃, aligning with their role in stimulating seed germination.</p>