Writing center tutors play a key role in advancing L2 writers' language learning because the tutorial interaction involves the introduction of new language and vocabulary at the point of need or interest. This tutor-research case study presents a detailed, complex portrait of how a second language writer in a US writing center learned and used vocabulary; how he employed his tutor's face-to-face and online feedback on his vocabulary errors to further his vocabulary learning; and how he perceived his vocabulary learning and his college learning in general. The study demonstrates the importance of extensive reading for learning new words as well as the complementarity of face-to-face and online feedback, especially to help with learning what is termed the lexicogrammatical component of words. (Contains 1 table and 1 figure.)