This study complements previous research on linguistic features of English as a lingua franca (ELF) from a syntactic complexity perspective. Specifically, the present study seeks to find out how ELF users express meaning relations in research articles using different syntactic structures. The same syntactic phenomena are also analyzed in comparable texts written in American English (AmE) to see in which way ELF writing is shaping research writing in English. Our findings show that the values of nine indices from four syntactic complexity dimensions in ELF research articles are significantly different from those in comparable AmE research articles. ELF authors use longer sentences to improve communication efficiency, and more coordinate phrases and complex nominals to enhance clarity and to increase explicitness. In addition, considering phrasal complexity, ELF research articles show greater reliance on nominal phrases in comparison to AmE articles. In other words, the convention of a nominal style is valued in ELF academic written discourse. These features of syntactic complexity illustrate writers’ handling of two competing goals, explicitness and conciseness, in the ELF academic writing. This study is significant in that it offers insights to the description of the emerging use of ELF in academic written discourse.