Sixty-five Japanese learners of English participated in the current study, which investigated the acquisitional value of form-focused instruction (FFI) with and without corrective feedback (CF) on learners' pronunciation development. All students received a 4-hr FFI treatment designed to encourage them to notice and practice the target feature of English /[alveolar approximant]/ in meaningful discourse, except those in the control group (n = 11), who received comparable instruction but without FFI on English /[alveolar approximant]/. During FFI, the instructors provided CF only to students in the FFI + CF group (n= 29) by recasting their mispronunciation or unclear pronunciation of /[alveolar approximant]/, whereas no CF was provided to those in the FFI-only group (n = 25). Acoustic analyses were conducted on frequency values of the third formant (F3) of English /[alveolar approximant]/ tokens elicited via pretest and posttest measures targeting familiar items and a generalizability test targeting unfamiliar items. The results showed that: (a) F3 values of the FFI + CF group significantly declined after the intervention, not only at a controlled-speech level but also a spontaneous-speech level, regardless of following vowel contexts; (b) change in F3 values of the FFI-only group and the control group was not statistically significant; and (c) the generalizability of FFI to novel tokens remained unclear.