To investigate the use of disagreement speech acts in Korean, this study compared and analyzed data collected through the Discourse Completion Test (DCT) in September 2023 for 30 Chinese advanced Korean learners and 30 native Korean speakers. The characteristics and differences in the use of such acts between Chinese and Koreans were identified. In addition, to determine whether the influence of native language is responsible for these differences, we conducted a DCT in Chinese on 25 Chinese learners and examined the patterns of use of the aforementioned acts. This study derived the following results. First, the response type to the disagreement speech act was “presenting a conflicting opinion” in 45.1% and 33.2% of advanced Chinese learners and native speakers, respectively. Second, the pattern of unsympathetic disagreement appeared at a higher rate in Chinese learners, while that of empathic disagreement appeared at a higher rate in native Korean speakers. Among empathic disagreements, Koreans (27.2%) used “response” more than Chinese (11.3%), and “recognition/understanding” was also used more often by Koreans (18.8%) than Chinese (13.6%). Third, even when using the same disagreement speech act, the expression methods of Chinese and Korean people were different. In the case of the latter, they used various methods together and expressions that gave the other person a softer feeling, whereas the former expressed their opinions or thoughts directly. Fourth, when comparing when Chinese learners perform disagreement speech acts in Chinese and Korean, they used more empathic and considerate content when expressing in Chinese in the same situation. We compared the disagreement speech acts of Chinese Korean language learners with those of native Korean speakers and identified the differences, thus providing implications for education on disagreement speech acts.