The objective of this study was to identify whether there are any homogeneous subclasses of teachers exhibiting different profiles of barriers to implementing ESD among Korean secondary teachers, and to examine whether teachers’ experiences of taking an ESD course in their pre-service teacher education and in their in-service training on ESD are predictive of membership in subclasses of perceived barriers to implementing ESD. Korean secondary teachers from various subjects were selected as a sample. I carried out latent class analysis (LCA) on barrier variables and assessed the association of both the experiences of taking an ESD course in their pre-service teacher education and in-service training on ESD with membership in the latent subclasses using multi-nominal logistic regression. These analyses were performed using PROC LCA. Research results are as follows: Firstly, four latent classes were identified: the few barrier, the individual barrier, the combination of individual and class-driven structural barrier, and the combination of individual and structural barrier. Secondly, both the experiences of taking an ESD course in their pre-service teacher education and in-service training on ESD were significant predictors of latent class membership. The current study could potentially assist both pre-service teacher educational institutions and in-service teacher training organizations with strategies designed to improve ESD competency among teachers.