The identification of stressed syllables by adult second-language (L2) Spanish learners was examined for evidence of influence of an allophonic alternation driven by word position and stress. The Spanish voiced stop-approximant alternation, whereby stops occur in stressed-syllable and word onsets, was utilized. If L2 learners track the distribution of this alternation, they should tend to link stops to stressed syllables in word-onset position and approximants to unstressed, word-medial position. Low- and high-intermediate-level first-language English learners of Spanish as well as native Spanish and monolingual English speakers listened to a series of nonce words and determined which of the two consonant-vowel (CV) syllables they perceived as stressed. In Experiment 1, onset allophone and vowel stress were crossed. In Experiment 2, the onset allophone alternated and a vowel unmarked for prominence was used. The results show that the monolingual English and low-intermediate groups were more likely to perceive syllables with stressed vowels as stressed, regardless of the allophone onset. In contrast, listeners with greater Spanish proficiency performed similarly to native Spanish speakers and were more likely to perceive stress on syllables with stop onsets, a pattern that follows the distributional information of Spanish. This finding suggests that learning the interplay between allophonic distributions and their conditioning factors is possible with experience and that knowledge of this relationship plays a role in the acquisition of L2 allophones.