Second language learners’ (L2ers’) perception and production of consonant clusters is influenced by the syllable structure of the native language (L1). This study investigates whether the perception of epenthetic vowels is partially responsible for why Spanish speakers have difficulty producing /s/ + Consonant (“sC”) clusters in English, and whether it affects word recognition in continuous speech. Spanish, German L2ers of English, and native English speakers completed: (i) an AXB task with (/ə/)sC-initial nonce words (e.g., [əsman]-[sman]); (ii) a word monitoring task with (/ə/)sC-initial words in semantically ambiguous sentences (e.g., I have lived in that (e)state for a long time); and (iii) a production task with the same sentences as in (i). L2ers also took a word-familiarity rating task and a cloze test to assess their proficiency. For (i) and (ii), accuracy rates were recorded, and response times were measured from target onset. For (iii), acoustic analyses showed whether the L2ers’ productions of sC-initial words contained an epenthetic vowel. Preliminary results suggest that perception difficulties may be partially responsible for Spanish speakers’ production and word-recognition difficulties with sC-clusters in English, but production data suggest that articulatory problems may also play an important role. Proficiency does not seem to help overcome this difficulty.