This study examined the acquisition of Korean stop sounds /t/(ㄷ), /t’/(ㄸ), and /th/(ㅌ) by Indonesian learners of Korean using a behavioral experiment called AX Discrimination Task, and voice production test analyzed by Praat. Nineteen advanced learners and nineteen intermediate learners participated in both tasks. Result of AX discrimination task showed that Indonesian learners were significantly less accurate than native speakers of Korean, and intermediate learners were significantly less accurate than advanced learners in discriminating /t/(ㄷ), /t’/(ㄸ), and /th/(ㅌ). Besides, in terms of reaction time, intermediate learners were the slowest participants in recognizing /t/(ㄷ), /t’/(ㄸ), and /th/(ㅌ). Meanwhile, in the voice production test, both intermediate and advanced learners revealed significant differences in pronouncing /t/(ㄷ), /t’/(ㄸ), and /th/(ㅌ) compared to native Korean. The results of this study showed in perceiving and producing Korean stop sounds /t/(ㄷ), /t’/(ㄸ), and /th/(ㅌ) between the Indonesian learners and native Korean. Overall, this study indicates that in terms of perceiving and producing Korean stop sounds /t/(ㄷ), /t’/(ㄸ), and /th/(ㅌ), and advanced learners shows an increase than intermediate learners, this indirectly proves that lower proficiency predicts lower pronunciation performance as claimed also by Higgs and Cliford’s(1982) on their relative contribution model. This study also revealed similar results with previous studies, where basic, intermediate and advance learners showed significant difference in perceiving and producing Korean stop sounds, while intermediate or advanced learners showed perceiving and producing Korean stop sound that was much closer to that of native Korean(Kim, 2012; Kim, 2006).