The sociolinguistic phenomenon of codeswitching, both diglossic and bilingual (Arabic–Hebrew), is extremely pervasive in all varieties of Palestinian Arabic, including Negev Arabic. Surprisingly, neither of these types of codeswitching in Palestinian Arabic has received due scholarly attention; moreover, their interplay has not been studied for any type of Arabic. This article analyses quantitative and functional aspects of diglossic and bilingual codeswitching in the personal interview style of 11 Negev Bedouin female students, focusing on their functional interaction. In the five distinct registers analysed, ratios of both diglossic and bilingual codeswitching were found to rise from childhood narratives to recounts of the period of academic studies and expository sections, with the use of Hebraisms dropping in the more formal registers. Although mixed bilingual discourse with intensive codeswitching is the default style for in-group discourse of the young generation, I show that many switches are not random, but fulfil discourse-pragmatic, communicative, social and textual functions typical of each of the registers. For example, in the narrative registers, switching may mark evaluation (commenting, explaining, self-repair, sidetracking, repetition). In both narrative and non-narrative discourse it may mark quotations, rephrasing or paraphrasing, with or without a metalinguistic introducing particle such as ‘as they say’. The result is redundancy at the referential level, with pragmatic functions of emphasizing or elaborating at the discourse level. This is in keeping with functions identified for bilingual codeswitching in general and also for diglossic codeswitching in Arabic; but it is the first effort, as far as I know, to combine analysis of the two codeswitching dimensions in any given code; and, moreover, to study the interplay of this bi-dimensional switching with relation to the stylistic factors of genre and register.