The present study investigated the effect of global warming on germination and initial growth across six deciduous oak species (Quercus mongolica, Q. variabilis, Q. serrata, Q. dentata, Q. aliena, and Q. acutissima), which are the dominant tree species in Korea forest ecosystems. Seeds were sown in climate change treatments, with temperatures higher than those of the control (approximately 3.0°C higher), and CO2 concentrations higher than those of the control (approximately 2-fold higher). Initial growth in each species was measured every two weeks. Initial growth was more rapid in all oak species at the time of root and shoot emergence under high temperature and CO2 treatments than in the control group. Leaf emergence in Q. mongolica, Q. variabilis, and Q. serrata occurred earlier under the climate change treatments than under the control. Root length increased significantly in Q. mongolica, Q. variabilis, and Q. dentata under the climate change treatments when compared to under the control. However, Q. aliena and Q. serrata exhibited a contrasting trends, and no significant difference was observed between the species and Q. acutissima. Shoot length increased significantly in Q. aliena under climate change treatments when compared to under the control but decreased in Q. aliena. In addition, no significant difference was observed in shoot length among Q. mongolica, Q. dentata, and Q. acutissima. The results showed that climate change treatments facilitated early growth, rapid emergence from the ground, leaf development, and enhanced belowground growth in Q. mongolica. Conversely, Q. aliena exhibited the lowest aboveground and belowground growth under climate change treatments when compared to other oak species. Climate change treatments had the least impact on Q. acutissima considering the insignificant differences observed in initial growth rates under climate change treatment.