It has been said that teaching is the noblest and the most important profession in the world. Teaching is especially important to the nation because teaching is building the builders of the nation. No one can claim that he has no passed through the hands of a teacher or teachers. This study aims at identifying the competencies and performance of English teachers and students achievement and attitude. The data were requested from the TNU Management Information System’s Office. The data on Instructional performance were the data on Faculty Performance Evaluation administered by the Human Resource Management Office during the first semester of school year 2013-2014 using an instrument adopted from the study of Reyes (2002) and Javier (2008). The instrument consists of eight dimensions or competencies namely, subject matter expertise, instructional expertise, classroom management expertise, communication expertise, diagnostic expertise, and relational expertise. Each dimension consists of statements that describe the competency being assessed or a total of 10 statements. The subjects of this study included 60 full-time teachers of English at Thai Nguyen University. Based on the findings of this study, the following conclusions were drawn. (1) Teachers are considered competent based on the respondents assessment on their teaching performance. (2) Teachers’ instructional expertise in terms of subject matter is moderately competent; while they are considered competent in terms of classroom management, instructional, communication, diagnostic and relational expertise. (3) Subject matter, instructional and diagnostic expertises are highly significant on the teachers’ instructional performance. However, communication and relational expertise recorded only significant relationship on their performance. While, classroom management turned to be not significant on their instructional performance. Thereby, instructional plan is proposed for implementation and evaluation to improve the teaching learning process in English Language.