The major purpose of the study is to look at ethnic identity and language use of the heritage Koreans in the US. Twenty young heritage Koreans living in Hawaii were studied on how they identified their own ethnicity and what relations there would be between their ethnicity and their language use in bilingual contexts. The major findings in the study are as follows: 1) Almost half of them identified themselves as Korean and the other half as Korean-American, 2) Scarcely did they use Korean outside home, 3) Their ethnicity showed no clear difference in the use of Korean and language choice between Korean and English in some context, however it was related with their proficiency level of Korean, 4) The higher their proficiency level was, the more they used Korean and the more they switched English to Korean in their three minute talk, and 5) Their ethnicity showed a clear difference in code-switching to Korean in their three minute talk.