The study focused on improvement needs of teachers for effective teaching of Agricultural Science in Senior Secondary Schools in Bauchi State. Four research questions and four null hypotheses guided the study. Improvement needs of teachers of agricultural science under subject matter mastery, planning of instruction, and implementation of instrument and evaluation of instruction were reviewed. Many related empirical studies were also reviewed and none of them specifically focused on improvement needs of teachers for effective teaching of Agricultural Science in Senior Secondary School and none of them is carried out in Bauchi state. The population of this study was 344 Agricultural science teachers and supervisors in the state. A sample of 185 respondents was obtained using Taro Yamane formula. Improvement needs of teachers’ Questionnaire (INTQ) was developed and used for data collection. Three experts validated the instrument. Cronbach Alpha reliability coefficient of 0.81 and 0.78 were obtained for the two sets of instruments of teachers and supervisors. Weighted mean and improvement needed index (INI) were used to answer the research questions and Z-test statistics was used to test the null hypotheses at 0.05 level of significance. It was found out most teachers of Agricultural science in Senior Secondary School in the state required improvement in subject matter mastery, planning of instruction, and implementation of instruction as well as evaluation of instruction to be effective in teaching the students. This implied that many of the teachers cannot perform the teaching job as expected. It was recommended that needed competencies identified by the study be used to retrain teachers of Agricultural Science in Bauchi state through workshops and seminars.