The allophonic variation of coda /S/ in the Florianopolitan variety of Brazilian Portuguese shows explicit associations between [ʃ] and the local stereotype of native resident – one who was raised in Florianópolis whose parents were also raised in the area. We hypothesize that the aforementioned explicit association is an implicit association, that is, an unconscious and automatic one. We argue that an implicit association towards the native resident stereotype is a cognitive bias that affects how Florianopolitans perceive the speech of other Florianopolitans. The strength of the associations was verified in terms of participants’ linguistic background. In order to do so, an Implicit Association Test and an explicit task pairing the [ʃ]/[s] variants with the native/non-native resident stereotypes were applied to 30 Florianopolitans whose parents were native, non-native, or mixed-origin residents. We found that an implicit association is at play in a moderate fashion. However, linguistic background only predicted the explicit association. More important, the fact that Florianopolitans explicitly chose the guise containing [ʃ] as the most representative of the speech of the native resident – even though some participants reported that non-existent prosodic elements differentiated the guises – reinforces the role of implicit cognitive biases on the social perception of coda /S/.