This study examines syntactic complexity in Translated English (TE) and English as a Foreign Language (EFL), drawing comparisons with Native English (NE). The objective is to explore the unique syntactic features of these constrained languages, which we hypothesize are influenced by inherent cognitive and social constraints. We operationalize syntactic complexity using five constructs, namely length of production units, sentence complexity, subordination, coordination, and specific structures. The data reveals differential syntactic patterns across the language varieties studied. In our analysis, we observed that TE and EFL display a tendency for extended sentence structures, as indicated by higher mean lengths of clauses (MLC) and T-units (MLT) compared to NE. We propose that this inclination might stem from first-language interference in the writing and translation. The study also underscores a decrease in sentence complexity and subordination in constrained languages, a pattern which potentially mirrors the simplification phenomenon often reported in second language acquisition and translation research. Conversely, coordination measures exhibit an increase in TE and EFL, suggesting a syntax preference possibly informed by the linguistic structures of the speaker's or translator's first language. Our findings resonate with the idea of "constrained communication", illuminating shared syntactic tendencies between second languages (L2s) and translated languages, which may be attributable to similar processing constraints. This investigation contributes to the ongoing dialogue on complexity and simplification in constrained languages, and encourages a merger of the traditionally separate fields of second language acquisition and translation studies. • 14 syntactic complexity metrics were used to assess the complexity of native, EFL, and translational varieties. • The translated and EFL varieties consistently diverge in complexity from the native variety. • The native variety tends to utilize more subordination compared to the native English variety. • Compared to the native variety, translated and EFL varieties tend to use more coordinate phrases. [ABSTRACT FROM AUTHOR]