This study investigated the impact of staff development programmes on the performance of teachers in secondary schools in Asaba Metropolis in Delta State, Nigeria. Six objectives were formulated among which are to: examine the impact of in-service training on the performance of teachers in secondary schools and ascertain the impact of conference on the performance of teachers in secondary schools. Six research questions and six hypotheses were also formulated in line with the objectives of the study. The research design used for this study is descriptive survey design. The population of the study comprises 31 supervisors, 64 principals and 1814 teachers, making the total of 1909. Stratified sampling technique was used to determine the sample size in case of principals, teachers and zonal educational supervisors, the sample used for the study are 6 principals, 10 supervisors and 203 teachers making the total of 219 respondents. A self-developed questionnaire was used to collect relevant data. The instrument was validated by the researcher?s supervisors and other experts in the department of Educational Foundations and Curriculum. The instrument was pilot tested and a reliability index of 0.945 was obtained. The six (6) hypotheses formulated for the study were tested using Analysis of Variance (ANOVA). Five null hypotheses were accepted (retained) and one was rejected. The results showed that in-service training, conferences, seminars, symposium and mentoring have improved the performance of teachers in secondary schools in Asaba Metropolis in Delta State. However, from the findings, it revealed that workshops were not properly carried out by the teachers in secondary schools in Asaba Metropolis that led to the rejection of the hypothesis. In view of the findings of the study, recommendations were made among which were that government and school administrators should encourage teachers in secondary schools in Asaba Metropolis to go for in-service training in order to enhance high performance in the classroom. Also, Policy on the conduct of conference should be strengthened to enable teachers benefit further from such training because of its effectiveness on the performance of teachers in secondary schools in Asaba Metropolis, Delta State.