This study investigated Korean heritage language (KHL) learners' foreign language classroom anxiety, reading anxiety and writing anxiety using the Foreign Language Classroom Anxiety Scale (FLCAS) by Horwitz, Horwitz and Cope, the Foreign Language Reading Anxiety Scale (FLRAS) by Saito, Garza and Horwitz and the Writing Apprehension Test (WAT) by Daly and Miller. Sixty-one KHL students enrolled in a heritage-track second semester Korean course at a large university in the southwest USA participated. The results showed that the KHL students generally showed low or moderate levels of foreign language anxiety and reading anxiety and a relatively high level of writing anxiety. In addition, the FLCAS had highly positive correlations with the FLRAS and the WAT, indicating that students who had high anxiety about foreign language learning in the classroom also had high levels of reading and writing anxiety. All three types of anxiety correlated negatively with student achievement, that is, students with high anxiety had lower grades. Moreover, significant differences existed between two groups based on perceived cultural ethnicity, indicating that KHL students who identified themselves as Korean showed significantly lower levels of anxiety and had higher grades than KHL students who perceived their cultural identity as American.