This study examines common claims associated with shadowing. Studies in Japan conclude that shadowing is effective for improving learners' listening skills. Two common claims are that shadowing is effective for lower-proficiency learners and that it enhances learners' phoneme perception, thus improving listening comprehension skills. The former notion lacks sufficient research and the latter empirical data. Therefore, this study explores these claims by examining whether shadowing training improves learners' phoneme perception and listening comprehension skills, and whether its effectiveness is limited to lower-proficiency learners. Participants comprised 43 Japanese learners of English as a foreign language (EFL) from a Japanese national university. Nine lessons were conducted using an EFL textbook, following the teaching procedures outlined by previous studies. The pre- and post-tests utilized part of Japanese standardized tests for English listening (22 questions) and a 20-item dictation cloze test. Students were divided into low- and intermediate-proficiency groups using the listening pre-test results. Statistical analyses indicated that phoneme perception was enhanced in both groups, but only low-proficiency learners improved their scores for high-school level listening questions. Accordingly, language instructors may wish to use shadowing to improve learners' foreign language skills, especially for bottom-up processes in listening.