Despite the recognized importance of morphological knowledge to literacy outcomes such as vocabulary knowledge and reading comprehension, two of its subconstructs--morphological awareness and morphological processing--have received comparatively little attention. In response, the aim of the study reported here was to examine how the relationships between morphological awareness and morphological processing, especially in terms of morphological transparency and morphological frequency, contribute to the vocabulary knowledge and reading comprehension of 62 native Korean-speaking secondary school students--27 eighth-graders and 35 tenth-graders--learning English as a foreign language. The students' performance on the Test of Morphological Structure and the Word Reading Test was assessed to gauge their compounding awareness, inflectional awareness, vocabulary knowledge, and reading comprehension. The results indicated that the students' performance was varied depending on morphological transparency and frequency. In addition, it was not morphological processing, but rather morphological awareness that explained variances in vocabulary knowledge and reading comprehension, when compounding awareness and inflectional awareness were controlled for. This paper discusses what such findings imply for teaching English as a foreign language to Korean learners.