Explicit phonetics instruction can help second language (L2) learners to moderately improve their pronunciation, but less is known about how the instruction affects learners' perception, even though there is evidence that perception and pronunciation are related. This study provided phonetics instruction to students (n = 46) studying Spanish as a foreign language and measured the resulting change in their perception of eight target phones as compared with a control group (n = 41). Perception was assessed with discrimination tests immediately following instruction and three weeks later. Results indicated that the instruction conferred a small advantage in the delayed posttest and that course level was not a significant factor, suggesting that phonetics instruction was effective for attuning the perception of learners at multiple stages of development.