This study compares the syntactic complexity between translational and non-translational English across four genres (i.e. fiction, news, general prose, and academic prose) and examines the connections between various forms and degrees of syntactic complexity measures and explicitation. Fourteen syntactic complexity indices were examined based on a one-million-word translational English corpus (COTE) and a one-million-word non-translational English corpus (i.e. FLOB), respectively. This study shows that syntactic explicitation in translations varies with the formality of discourse. The most significant complexity difference between translational vis-à-vis non-translational English is found in fiction, which is regarded as the major contributor to translational English syntactic complexity. No significant difference in syntactic complexity was observed between the two types of academic English texts. Translational English news and general prose stand between fiction and academic texts. Translational fiction and news are characterised by more phrasal complexity features such as coordinate and complex nominal phrases, and a key indicator of translational English general prose complexity is subordination. The findings of this study will help students of translation to make informed decisions on the arrangement of sentence structures when given texts of different genres.