Within the scope of research that lies at the intersection of sociolinguistics and second language acquisition, there is a growing body of empirical work on learners’ acquisition of variable subject expression in Spanish. This research has been instrumental for demonstrating that second language (L2) learners acquire linguistic and social constraints on subject form use. The present study extends research on variable Spanish subject expression to an understudied learner population: native Korean-speaking learners. Interview data were examined for the range and frequency of first-person subject forms produced by Korean-speaking learners at four instructional levels as well as linguistic and individual (extralinguistic) predictors of subject use. Results showed that learners at each level produced primarily null subjects, and verb number, verb-form regularity, verb semantics, and use of Spanish outside of class significantly predicted use of an overt personal pronoun over null subjects.