The concept of Teacher Performance Appraisal and Development (TPAD) policy was officially operational zed in Kenya in 2016 with the main aim of improving the performance of teachers and consequently, academic achievement of pupils. Despite the good intentions of TPAD, pupils’ performance in Kenya certificate of primary education in Ndhiwa Sub County has been low despite the operationalization of TPAD in 2016 with mean scores of 241.66 in 2016, 238.93 in 2017, and 238.65 in 2018 and 238.92 in 2019. This necessitated the current study which explored the perspectives on the effect of TPAD on teachers` performance. The objective of the study was to determine perspectives on the effect of TPAD on professional knowledge application in public primary schools in Ndhiwa Sub County. The study established that Teacher Performance Appraisal and development policy had moderate effect on teacher professional knowledge application. This is because it enhanced the following aspects of knowledge application. This included: maintenance and use of schemes of work in teaching, maintenance and use of lesson plans that guide teachers in effectively managing lessons during lesson presentations, teachers’ ability to set examinations for pupils which is undertaken regularly, preparation and use of marking schemes by teachers to the expected standards, teachers’ commitment to timely marking of pupils formative examinations which are regularly administered to learners, teachers’ commitment to giving timely feedback to pupils on their academic performance in terms of weaknesses and strengths, maintenance and use of record of work covered, maintenance and use of pupils’ progress records, teachers’ commitment to regularly updating of lesson notes relevant to teaching, teachers’ organization of individualized education programmes for pupils, teachers’ effectiveness in invigilating formative and summative examinations, teachers’ ability in identification of weak learners in time and assisting them in improving academically. These findings are important to stakeholders in education particularly, the Ministry of Education, Kenya Institute of Curriculum Development, Teachers Service Commission, Kenya National Examination Council and Boards of Management in informing policy formulation relating to teacher professional knowledge application which is always at the centre of curriculum development and implementation.