Back ground: Acute kidney injury (AKI) is a rapid worsening or loss of kidney function that can be caused by a variety of different mechanisms. AKI is very common and under-recognized disease process, which carries a high risk of mortality and morbidity. About 2 million people die of AKI every year due to many factors including lack of understanding of AKI among health care workers. The recognition of risk factors and management of patients with AKI remains poor with only 50% of patients receiving optimal care. In both developed and developing countries, health care workers had difficulties in recognizing risk factors and identification of patients with AKI. This suggests the need to strengthen education on AKI among health care workers. Education needs are country specific. There is no similar data from Tanzania to inform such AKI education programs, hence our study. Objective: To assess level of knowledge of acute kidney injury among health care workers at different level of care in Moshi. Methodology: The study was facility-based cross-sectional study which was conducted from end of May to June 2016 in Moshi. The facilities include Majengo Health Centre, Pasua Health Center, St. Joseph designated district hospital, Kibosho designated district hospital, Mawenzi regional referral hospital and KCMC hospital which is a consultant zonal hospital. A sample of 384 health care workers was selected through multistage sampling. Data was collected through interview by using structured questionnaire and analysis was done through SPSS after creating a dataset through Microsoft Excel. Results: A total of 386 health care workers were enrolled. Their mean age was 37.2(SD±11.0) years. Out of 386 participants, only 3.9% had received AKI training. Only 2.3% of health care workers have a good knowledge to define AKI according to KDIGO system and majority (56.7%) have a good knowledge to mention three to five risk factors. About 17.1% have an adequate knowledge to categorized AKI correctly and 58% to recognize signs and symptoms of AKI. The health care workers who had know how to do bedside observation to the patient with AKI was 39.6%. Only 2.1% of interviewees did have adequate knowledge on when to refer to a nephrologist and 24.6% had knowledge on how to manage patient with AKI. Conclusion: This study shows a gap of knowledge among health care workers in Moshi on the basics of AKI risk factors, recognition and management. Majority of health care workers did not receive AKI training. Doctors and specialist had more knowledge on AKI risk factors and management. CO&AMO had more knowledge on AKI recognition. So still knowledge is needed to health care workers in order to reduce morbidity and mortality to the patients with AKI.