Tetun Dili is an Austronesian language and one of the two official languages in Timor-Leste, alongside Portuguese with which it has been in contact for centuries. In this detailed study, we describe various aspects of gender in Tetun Dili, in both native and borrowed vocabulary. We identify marked differences between gender marking in native and borrowed Portuguese words, with Tetun prioritizing the feminine, and Portuguese the masculine. We show that through contact with Portuguese, Tetun Dili has also developed "marginal" gender, with grammatical gender agreement being optional but increasingly common for Portuguese loans, mainly in the acrolect. Grammatical agreement is also spreading to a handful of non-Portuguese words, to which there is evidence of incipient grammatical gender assignment. Some comparisons are made with developments in Chamorro and Tagalog, two Austronesian languages heavily influenced by Spanish (closely related to Portuguese), for which gender contact effects have previously been described in some detail. We conclude with a set of more general typological observations.