Dissertation (MSc Nursing Education)Hazardous health care wastes cause unhealthy effects on people and the environment. However, no published study evidence about the training and competencies of hospital cleaners on health care waste management in Tanzania. Hence, the study aimed to assess the effectiveness of health care waste management training on improving competencies of hospital cleaners at Dodoma Regional Referral Hospital and Benjamin Mkapa Hospital in Dodoma Region. The study recruited 85 hospital cleaners and employed a quasi-experimental design without control. Systematic sampling was applied to select the study participants. Data were collected from June to August 2020 by structured interviewer-administered questionnaires and observation checklist at pre and post-intervention time. Data were analyzed using Statistical Package Software for Social Science version 26. Descriptive statistics were done to determine the frequencies and percentage distribution of demographic information and cross tabulation was performed to observe the relationship between the level of knowledge, attitude and level of practice against demographic characteristics and Chi-square test was reported. Inferential statistics were employed to determine the effectiveness of training on improving knowledge and practice of hospital cleaners whereby paired sample t test statistic was done. The p-value was set at two sided of less than 0.05. The study response rate was 100% (85/85) and the mean age of the study participants was 30.13±8.838 years. The baseline results showed minority of the study participants had adequate knowledge and good practice on health care waste management (14.1% and 2.4%) respectively while majority (70.6%) had positive attitude. Moreover, the mean knowledge scores, at the pre-test was 13.20±2.364 and post-test was 16.92±1.904 while the means practice score at pre-test was 2.95±2.95 and at posttest was 4.68 ±0.790. Further, the results of the paired sample t-test showed a significant difference between pre and post knowledge scores with the mean difference of (3.718,95%CI:3.113-4.322; p-value≤0.001) with the effect size of 0.6 whereas results showed a significant difference between pre and posttest practice score with the mean difference of (1.729,95%CI:1.484-1.975;p-value≤0.001) the effect size of 0.7. This study concludes that training on health care waste management is effective on improving the level of knowledge and practice on safely managing health care waste in hospitals. Therefore, the researcher recommends hospital cleaners to be trained on health care waste management before they start handling health care wastes.