The purpose of this study is to examine if there is a difference in learners` academic achievement (test areas: short sentence listening, long paragraphs listening, vocabulary and grammar, and reading) between NEST classes and non-NEST classes of college test-based English courses. The pre- and post-TOEIC scores of 493 college students taught by 13 NESTs and 429 students taught by 5 non-NESTs were analysed according to learners` English levels (above 800, in the 700s, in the 600s, in the 500s, in the 400s, below 300) and their fields (engineering, humanities, social sciences, commerce and economics, laws). The results of the analysis showed that vocabulary and grammar proficiency in high-level non-NESTs` classes, reading ability in low-level NESTs` classes, and short sentence listening ability in NSETs` commerce and economics classes statistically improved. No differences in other areas were found. The overall results of the study imply that both NESTs and non-NESTs could be equally successful in test-based courses regardless of levels and majors although more positive effects were obtained in terms of high-level learners` achievement in vocabulary and grammar areas taught by NESTs and low-level learners` achievement in reading areas taught by non-NESTs. Some pedagogical and research implications are suggested.