This study was about the effectiveness of teachers’ service department in promoting secondary school teachers moral and ethical values in Tanzania. It specifically focused on the factors contributing to teachers’ misconduct in their work station, the performance and effectiveness of teachers’ service department in promoting secondary school teachers moral and ethical values, the TSD challenges in promoting teachers moral and ethical values and alternative strategies for promoting teachers moral and ethical values. A case study design with both qualitative and quantitative approach was used in this study. Data collection methods used were questionnaires and interviews. A sample of 57 respondents was drawn from the target population. Both purposive and simple random sampling techniques were used in this study. The study revealed that the performance of TSD in promoting moral and ethical value was not effective. Furthermore the study revealed that; the reasons for deterioration of teachers moral and ethical value in Rufiji District Council were misunderstanding of what the codes address; low salaries; poor living and working conditions; lack of proper training related to professional; ineffective educational management; nature of entrants in professional; poor administration and lack of TSD professional workers. The study also indicated that, the forms of misconduct that mostly happen were sexual abuse, drunkenness, examination fraud, absenteeism and unethical dressing. Whereby, lack of fund to go and contact teachers, long lasting cases on violation of moral and ethics, lack of supporting material and moral problem of society were among the challenges which face TSD in promoting secondary school teachers’ moral and ethical values in Rufiji District council. The study recommends that, the government, educational stakeholder and TSD to participate fully in promoting moral and ethical value in secondary school and similar study should be conducted to other district of Tanzania to check how they do in promoting moral and ethical values.