The field of third language acquisition has gathered increased attention over the last three decades. However, phonological acquisition in an L3 is still relatively under-studied within the field, despite there likely being over a billion people regularly using an L3 worldwide. In this paper, we review experimental and theoretical studies of sequential L3 acquisition to date and aim to give implications for future L3 phonological acquisition research, laying the groundwork for advances in this area. According to the reviewed studies, it is necessary to adapt previous second language phonology models (i.e. SLM/SLM-r, PAM/PAM-L2, L2LP) into future L3 phonological research. Additionally, it is essential to expand the research scope and time scale to reflect linguistic diversity, age and education background of participants, and the processes of learning.