How to mediate language change through contact in East Timor: grammatical parallelism in Tetun Dili While Portuguese has been present in East Timor since the 1500s, its influence has always been most evident in Tetun Dili. Contact between the two languages was however mostly interrupted in 1975, only to be reinstated with renewed vigour after 1999, with Tetun Dili and Portuguese progressively replacing Indonesian in public life. Tetun DIli is a largely isolating language with little productive morphology. While borrowing from Portuguese is most keenly felt in the lexicon, there is increasing evidence of contact effects on other parts of Tetun Dili grammar, especially in syntactic patterning and structures. What is unusual about this phenomenon in TD is its frequent mediation through intermediate forms. In a process we term here 'grammatical parallelism' TD and Portuguese elements can appear together ‐ often retaining their original syntactic characteristics, as in example (b) ‐ alongside fully native (a) and fully borrowed (c) structures ‐ all with the same meaning: (a) iha Agustu nia laran 'during August' LOC August 3sg insides (possessed body part construction) (b) durante Agustu nia laran (Portuguese durante ‘during’ + possessed body part) (c) durante Agustu (Portuguese durante 'during' only) Using data drawn from a large‐scale corpus of Tetun Dili, we present and discuss specific examples of 'grammatical parallelism', including some which have led to entirely new native structures developing within the last 10 years. We also consider some general characteristics of as well as possible reasons for grammatical parallelism in Tetun Dili.