A Dissertation Submitted in Partial Fulfillment of the Requirements for the Award of the Degree of Master of Science in Human Resource Management (MSc-HRM) of Mzumbe University Dar es Salaam Campus College.This study assessed the effectiveness of ethics on public service delivery at the Immigration Headquarters Dar es Salaam. In particular, the study focused on the unethical behaviours of the public servants on how they influence the service delivery at the headquarters Dar es Salaam. The methodology was a case study design. The study was conducted at the Immigration office Headquarters Dar es Salaam between June and mid July 2014. The study involved 40 purposively and randomly selected public servants who included 5 commissioners, 10 Heads of units of the Immigration service, 16 Immigration officers and 9 Immigration staff. Data was collected by using two instruments namely; Survey questionnaires and face-to face interview. The findings of the study revealed that a significant number of public servants at the Immigration office Headquarter were aware of the codes of ethics and codes of conducts. Furthermore another significant number of public servants at the Immigration Headquarters Dar es Salaam promote public service code of ethics principles. However it was found that some of the public servants still showed unethical practices such as favouritism, lack of accountability, irresponsibility, lack of professionalism, corruption, not being transparency, unfairness and self centeredness/egoism. This affected the smooth service delivery at the Immigration office Headquarters. The study recommended that the government should ensure that codes of ethics and codes of conduct are observed by every public servant in the office. In addition the government should give adequate training and good leadership to the public servants in the country.