This study aimed at ascertaining the impact of performance appraisal system on secondary school teachers‟ work performance in Tanzania. It also aimed at investigating the relation between reward and teachers‟ performance. This study involved both public as well as private secondary schools within Geita Township. Data were collected by use of questionnaires and interview guides. The questionnaires covered questions on performance appraisal criteria, attitude and perception, effectiveness of performance appraisal and satisfaction aspect. The questions touched several issues such as motivation, promotion, organization, discipline and pay increases. A sample size of 110 teachers, 5 private school managers and other 4 council officials was targeted to be involved in the study. However, a sample of 103 respondents was available for the study. The Statistical Package for Social Science (SPSS) and Microsoft Excel computer programmes were used in analysis of frequencies, percentage, mean, and Pearson correlation coefficient in data analysis.