Speakers vary in their pronunciations of the sounds in their native language. Listeners use lexical knowledge to adjust their phonetic categories to speakers' idiosyncratic pronunciations. Lexical information can, however, be inconclusive or become available too late to guide this phonetic retuning. Sentence context is known to affect lexical processing, and listeners are typically more likely to categorize steps of a phonetic continuum in line with the semantic content of a sentence. In a series of experiments, we tested whether preceding sentence context can guide phonetic retuning. During a passive-listening exposure phase, English listeners heard a sound ambiguous between /s/ and /f/ spliced into the onset position of minimal word pairs (e.g., "sin" vs. "fin"). Sentence context disambiguated these minimal pairs as /s/-initial for 1 group of listeners and as /f/-initial for another group. At subsequent test, listeners categorized more steps on a /sa/-/fa/ continuum in line with their prior exposure; that is, when sentence context had disambiguated the ambiguous sound during exposure as /s/, listeners gave more /s/ responses than /f/ responses at test. These aftereffects occurred independently of whether contrastive phonemes from the respective other category were provided. No phonetic retuning was found when the disambiguating sentence contexts were replaced with neutral ones. Overall, these results provide evidence that sentence context can guide phonetic retuning, therefore expanding the usefulness of phonetic retuning as a tool for listeners to accommodate speakers.