The purpose of this study is to investigate the sources of foreign language anxiety experienced by non-native pre-service ESL teachers (NNPSET) in licensure program. 52 pre-service ESL teachers enrolled in a public university in Seoul, South Korea, participated in this study during their teaching practicum as part of requirement to pursue ESL licensure. 52 participants completed a 24-item modified survey based on Foreign Language Classroom Anxiety Scale (FLCAS) in order to figure out 1) which language anxiety factors would be the most influential among NNPSETs in their English practicum, and 2) which language anxiety factors strongly affect NNPSETs when they conduct micro-teaching sessions. The Principal Component and principal axis factoring tools were used to analyze the data of the survey. The results indicate that 4 major factors were found which affected NNPSETs language anxiety on the classroom situation. The most influential factor of all was clustered with Factor 1 – ‘Language anxiety on using English in the class’. And the other three factors were identified as ‘Language anxiety based on self-confidence’, ‘Language anxiety about class preparation’, and ‘Language anxiety overcome with efforts’.