In spite of the increased interest in third language acquisition (TLA) in recent years, the field is still at the beginning stage. Considering the more interconnected society and the need for learning additional languages, there is an urgent need for more research into third language learning process or multilingual acquisition process. The purpose of this current study is to review existing empirical research on multilingual acquisition, focusing on whether monolinguals or bilinguals/multilinguals show differences in the multilingual acquisition processes. Although contradictory results of these empirical studies reveal the complexity of TLA, the current studys review of TLA studies suggest two points to be considered in the third language learning process: the need for precisely defining bilingual-multilingual and for considering variables of typological similarity, language proficiency and age. However, the limited settings of the studies constrain their conclusions and limitations, thus requiring further studies in other contexts and backgrounds.