The orthographic forms (spellings) of second language (L2) words and sounds affect the pronunciation and awareness of L2 sounds, even after lengthy naturalistic exposure. This study investigated whether instruction could reduce the effects of English orthographic forms on Italian native speakers’ pronunciation and awareness of L2 English sounds. Italians perceive, produce, and judge the same sound as a short sound if it is spelled with one letter and as a long sound if it is spelled with a digraph, due to L1 Italian grapheme-phoneme correspondence (GPC) rules whereby double consonant letters represent long consonants. Totally, 100 Italian learners of English were allocated to two conditions (final n = 88). The participants in the explicit GPC (EGPC) condition discovered English GPC rules relating to sound length through reflection, explicit teaching, and practice; the participants in the passive exposure condition practiced the same words as the EGPC participants, but with no mention of GPCs. Pre- and postintervention production (delayed word repetition) and phonological awareness (rhyme judgment) tasks revealed no positive effects of the instruction. GPC instruction appears to be ineffective in reducing orthographic effects on L2 phonology. Orthographic effects may be impervious to change, whether by naturalistic exposure or by instruction.