Native speakers tend to mirror the phrases and structures of interlocutors, which is known as alignment. Alignment is likely the result of an automatic process that facilitates speakers' mutual understanding as well as a strategic process influenced by social affective factors, such as the level of familiarity between interlocutors. However, the extent to which second language (L2) learners exhibit these effects remains unclear. Additionally, there is limited knowledge about how L2 alignment behavior relates to L2 learners' interaction patterns in their mother tongue. This study aimed to address these gaps by comparing the alignment of bigrams (word pairs) and task-oriented structures between familiar and unfamiliar peers in map task dialogues. We tested three groups of speakers (i.e., Chinese native speakers, English native speakers, and Chinese-speaking learners of English). Both native speakers and L2 learners aligned with their interlocutors, but L2 learners exhibited greater bigram alignment and L1 speakers displayed greater alignment of task-oriented structures. Furthermore, L2 learners were more likely to reuse unfamiliar interlocutors' bigrams as compared with familiar interlocutors. Interlocutor familiarity did not modulate the alignment rate in either L1 English or L1 Chinese. We conclude that L2 alignment might be strategic to some extent, whereas native speakers' alignment may be highly automatic.