The purpose of this study was to develop and validate a Self-assessment Instrument for Teacher Evaluation (SITE II) based on five National Professional Standards for Teachers developed by the Ministry of Education, Pakistan: subject matter knowledge, instructional planning and strategies, assessment, learning environment, and effective communication. The data were collected from 279 English and mathematics teachers of grade 10 in 40 public boys’ and girls’ high schools in district Okara who self-evaluated their performance on five teacher performance components. The overall reliability of the questionnaire was found high (α=.94). The SITE II factor structure was discovered through exploratory factor analysis. Confirmatory factor analyses provided evidence of construct validity of the questionnaire. Significant positive relationship was found between teachers’ scores on self-evaluation questionnaire and their students’ achievement (n= 7245) in English as well as in mathematics. The findings suggest that the questionnaire is valid and efficient tool for measuring components of teacher self-assessment. Teachers can use this scale for evaluation of their won teaching and take remedial actions. Mentors and supervisors can use it for diagnostic purpose and designing professional development courses for teachers.