Along with advanced globalization and multilingualism, there is a growing interest in the learning of Languages Other Than English (LOTEs) and simultaneous multiple languages. This current research delves into the motivation for learning Korean and simultaneous multiple languages among Chinese undergraduate students. To be more specific, the social and situated factors associated with the future self-guides of Korean language learning will be examined and the overall intended effort to learn the named languages L2 English and L3 Korean of simultaneous multiple language learners will be explored within the framework of L2 Motivational Self System. Two questionnaires were employed to address the research questions. The first questionnaire pertains to the simultaneous multiple language learners’ motivation to learn Korean, with the focus on the dynamic patterns among students at two grade levels in Korean language learning as well as their future self-guides to learn Korean language. The second questionnaire concentrates on the overall intended effort to learn L2 English and L3 Korean. The validity of both instruments in the Chinese context has been established. Subjects of the two studies are enrolled in a Sino-Korean joint-education program hosted in a Chinese university. The research results reveal that several variables, including family influence, cultural interest, attitude to learning Korean are differentiate between first-year Korean learners and second-year Korean learners. Second-year learners tend to mark higher in family influence and cultural interest, but show lower level of attitude to learning Korean. Variables including family influence, instrumentality promotion, instrumentality prevention, attitude to learning Korean, attitude toward Korean community and integrativeness are found to be correlated with the two self-guides for Korean language learning. In addition, the impeding influence of Korean learning experience on motivation to learn English has been identified. This research contributes to the expanding body of knowledge in the field of L2 motivation by exploring motivation for Korean language learning and simultaneous multiple language learning. Furthermore, it demonstrates the explanatory power of the L2 Motivational Self System within the field of simultaneous multiple language learning. These findings give rise to pedagogical implications that can offer insights into the realm of multiple language teaching and learning.