High vowel devoicing in Japanese, where /i, u/ in a C1VC2 sequence devoice when both C1 and C2 are voiceless, has been studied extensively, but factors that contribute to the devoiced vowels' likelihood of complete deletion is still debated. This study examines the effects of phonotactic predictability on the deletion of devoiced vowels. Native Tokyo Japanese speakers (N = 22) were recorded in a sound-attenuated booth reading sentences containing lexical stimuli. C1 of the stimuli were /k, ʃ/, after which either high vowel can occur, and /ʧ, ϕ, s, ç/, after which only one of the two occurs. C2 was always a stop. C1 duration and center of gravity (COG), the amplitude weighted mean of frequencies present in a signal, were measured. Duration results show that devoicing lengthens only non-fricatives, while it has either no effect or a shortening effect on fricatives. COG results show that coarticulatory effects of devoiced vowels are evident in /k, ʃ/ but not in /ʧ, ϕ, s, ç/. Devoiced high vowels, therefore, seem to be more likely to delete when the vowel is phonotactically predictable than when it is unpredictable.