The current study explores the effects that learners’ perceptions of text difficulty have on L2 outcomes and learning attitudes, focusing on Korean college students. One-hundred and twenty-seven learners were assigned to low-, medium-, and high-level groups based on their perceptions of English text difficulty. The study employed a background questionnaire, pre- and post-English tests, and pre- and post-language learning attitude questionnaires. The results of the study revealed that learners who wanted a more challenging level of text-difficulty outperformed those who did not in terms of English achievement. The findings also showed that two groups, the medium- and high-level groups, did not exhibit significant differences regarding English knowledge gains based on their expressed preferences for an advanced level course. As for learners’ attitudes, the three groups gave similar responses to a learning attitudes questionnaire that assessed the effectiveness of optimally challenging course levels on their language competence, their current proficiency levels, and learning confidence in future English learning. Based on those findings, suggestions are given for practitioners to implement into EFL classrooms.