This study examines the gender assignment strategies used in Gernika Basque (Basque Country, Spain) in Basque/Spanish mixed Determiner Phrases. Twenty-one simultaneous Basque/Spanish bilinguals completed a survey that comprised an Acceptability Judgment Task of code-switched sentences that they rated on a 1-7 Likert scale, a Forced-choice task, a Basque and a Spanish proficiency test, and a linguistic background questionnaire. Results from two Linear Mixed Models revealed that participants use two gender assignment strategies. In general, the bilinguals from Gernika that we studied preferred to assign the Spanish masculine determiner, el, to most Basque nouns. However, there is an exception when the Basque noun ends in lexical a. In these cases, they preferred to assign the Spanish feminine determiner, la, potentially as a result of homophony with the canonical ending for Spanish feminine nouns, also a. Additionally, they strongly dispreferred "double determiner constructions" (i.e. mixed DPs with both the Basque and the Spanish determiner). The gender assignment strategies used by simultaneous bilinguals from the Gernika region align with those used by English/Spanish simultaneous bilinguals, as reported in Liceras et al. (2008). However, our results contrast with what Parafita-Couto et al. (2015) found for the same language pair; we discuss these differences and explore a possible explanation for them in our discussion section.