This study that has taken place at an English-language center in Jakarta comprises an analysis of the relationship between the teachers competence and the students' achievements in a final-term test. The research concludes that there is positive correlation between the teachers' competence (independent variable) and the students' achievements (dependent variable). The teachers' competence covers three sub-variables: the teachers' attitude, teaching skills and language competence. The coefficient correlation between the teachers' competence and the students' achievements is .760; and respectively, the coefficient correlation between each sub-variable of the teachers' competence and the students' achievements are as follows: .595, .632, and .152. Therefore, the contribution of teachers' attitude toward the students' achievements is 35%, the contribution of teaching skills is 40% and the contribution of language competence is 2.3%. Altogether, the three sub-variables contribute 57% towards the students' achievements, and the rest is determined by other variables. Regarding the significance of the teachers' competence: it should be taken into consideration to enhance the students' achievements. In other words, the students' achievements can be improved through the improvement of the teachers' competence.