The present study investigated Korean-accented English (KoE) intelligibility and conducted experiments in Korea, Japan, and the USA to test the benefits of listener’s familiarity and identify the key phonological features of KoE. In the experiments, the participants were asked to transcribe the target (KoE) of 100 English statements each containing a target word representing one of the nine features. The transcription data were administered to four groups, depending upon the degree of KoE familiarity (length of exposure). The results indicated that KoE was most intelligible to native English speakers with lower familiarity and least intelligible to the Japanese participants with low KoE familiarity. Although the listeners’ familiarity did not necessarily either facilitate or impede the intelligibility of KoE, the listeners with higher familiarity with KoE tended to recognize the voiced consonants of KoE better. The findings also indicated which KoE characteristics affected the overall intelligibility level, suggesting ways to prioritize KoE features in English language learning in Korean classrooms.