In English, a relative clause (rc) follows the head noun phrase (np). Conversely, the rc in Chinese precedes the head np directly before it or is separated by a determiner phrase (dp). This is uncommon in the subject-verb-object order language and results in two types of constructions. For Chinese as foreign language (cfl) learners, this construction alternation is complex to acquire and is dependent on many factors. This study aims to explore the underlying factors influencing cfl learners’ outer modifier nominal (omn)/inner modifier nominal (imn) alternation and whether they have multiple interactions. A multifactorial exploration of the significant predictors of the omn/imn alternation in Chinese interlanguage data, taken from the International Chinese Interlanguage Corpus, was conducted. Conditional inference trees and random forests were used to analyse the data. The predictors studied consist of head np animacy (HeadNPAnimacy), head np length (HeadNPLength), grammatical roles of head nps in matrix clauses (HeadNPMatRole), grammatical roles of head nps in rcs (HeadNPRelRole), length of rcs (RCLength), types of native languages (NLType), and learners’ Chinese proficiency (CHProficiency). Examinations of omn/imn alternation show predictors’ significant effects in descending order of their effect size: HeadNPRelRole, HeadNPMatRole, RCLength, NLType, and HeadNPAnimacy.