Deputy principals play a crucial role in the management of secondary schools. Yet, their performance is often a product of diverse factors, among them being the pressure exerted from frequent performance appraisals. The study investigated the influence of techniques adopted for performance appraisal on the work output of deputy principals in public secondary schools in Nandi-North Sub-County, Kenya. The study was guided by Scientific Management Theory and used ex-post facto design. The target population included 55 principals, 67 deputy principals, and 1197 students of Form Three. Stratified and simple random sampling was used to sample schools and the respondents. The sample size was 328, comprising 16 principals, 21 deputy principals, and 291 students. Data was collected using questionnaires and analysed using both descriptive statistics and inferential statistics. The hypothesis was tested using an independent t-test. The study found a significant relationship between techniques of performance appraisal and the performance of deputy principals. Effective implementation of the techniques of performance appraisal could lead to the improved job performance of the deputy principals. Nevertheless, the performance of the deputy principals had a lower rating, particularly on the evaluation of classroom presentation, development of performance improvement plan and effective provision of feedback after evaluation after performance appraisal. It is recommended that performance appraisal techniques should be tailored to meet the unique environment in which deputy principals operate. The study findings are beneficial to the Teachers Service Commission, as the policy maker at the national level, in providing insights on the role of the performance appraisal system and how to effectively monitor and assess the performance of the deputy principals