Although Native English-Speaking Teachers (NESTs) are extensively utilized, very little is known about the impact of these teachers on speaking or writing in Asian contexts like South Korea. The purpose of this study was to examine the impact of NEST instruction on EFL learners' speech in a South Korean context. First, proficiency level of 100 learners was compared to amount of learning with a native English speaker using the Spearman rank correlation coefficient (rs [100] = 0.26, p = 0.01). Second, type/token ratios (variety of vocabulary) from 144 speeches of advanced learners were compared to amount of native-speaking instruction using the Spearman rank correlation coefficient (r[subscript s] [144] = 0.18, p = 0.03). Results suggest that native English instruction does indeed have some impact. Higher proficiency learners had more native instruction. Furthermore, advanced learners with more NEST instruction had more lexical sophistication of speech. While significant, correlations may not justify massive expenditures in an EFL context. Instead, results may reveal needs for change of curricula and pedagogical style.