This study investigates how Korean EFL learners use English conjunctive adverbials in college academic writing and what factors influence their use. This study conducts a quantitative study on the use of conjunctive adverbials by making a learner corpus. The data are collected from 70 Korean college students and their production is analyzed with a quantitative measure and corpus analysis. First, the result presents that the use of conjunctive adverbials by Korean EFL learners appears to be influenced by their English proficiency. The students who have higher English proficiency use conjunctive adverbials more frequently. Next, it is found that their use of conjunctive adverbials may be associated with the features of L1 regarding the classification of adverbials which is different from that of English. In addition, the results of this study are compared with those of the EFL learners from other countries based on the previous studies. Comparing with them, it is found that Korean EFL learners overuse the conjunctive adverbials in a resultive semantic relation (e.g., so) like Chinese and Arabic EFL learners, but unlike that of the EFL learners from other countries, the Korean learners show their preference of conjunctive adverbials in enumerative, additive, and contrastive semantic relations. Consequently, it can be concluded that the results shown by Korean EFL learners are due to differences in English proficiency and L1 transfer. Therefore, although conjunctive adverbials account for a small proportion of all sentences, it is essential to make up for English education materials for adverbials-related educational content to improve English writing skills for EFL learners.