Both Korean and Japanese have borrowed heavily from other languages (especially English), and much of this loanword vocabulary shows surprising similarity in meaning, grammar and form. In colonial Korea, Japanese loanwords were taught directly through Japanese-style education. This explains the similarity of prewar vocabulary, but this cannot be true of postwar vocabulary. After a brief historical review, this article presents a survey of the phonological, morphological (shortening, acronymization, and hybridization), semantic (shift and creativity), and grammatical (treatment of plurality and other markers) similarities between the two vocabularies. It is concluded that both historical and linguistic relationships between Japanese and Korean have affected JE (Japanese English) and KE (Korean English) where they differ from US English and that in some cases, it is general linguistic similarity that causes them to use the same forms, and in other cases it is due to influence of prewar borrowing patterns. It is also noted that the decorative function of English in both Korea and Japan plays an important role in the similarity of JE and KE, but detailed treatment is beyond the scope of this paper.