Scores from TEPS (Test of English Proficiency developed by Seoul National University) and TOEIC (Test of English for International Communication) are widely used in Korea for various purposes, including employment, admission, and certification. However, there is more than one score conversion relationship between these two tests, causing confusion among test takers. Moreover, the conversion relationships were established in 2004 and 2011 and have not been updated since then. With this background, a large-scale score comparability study was undertaken to develop a new score conversion table for TEPS and TOEIC. Data were collected from a total of 1,415 test takers using a single group design. Log-linear presmoothing and equipercentile methods were used for linking, with cross validation across subgroups. Results showed that the old conversions were disadvantageous to a certain test-taker group. A new conversion table between the two tests is then suggested.