Dissertation (MSc Public Health)The resistance to insecticides among malaria vectors poses a global challenge in the efforts towards malaria elimination. This calls for an addition of larval control methods such as biolarviciding. However, the implementation of biolarviciding in Tanzania has been very low. Therefore, this study explored factors affecting the implementation of biolarviciding in the councils of Southern Tanzania. A mixed-method, cross-sectional design was used to collect quantitative data from 400 community members and 12 Vectors Control Officers using structured-questionnaire and qualitative data through interviews with 37 key informants and document review of implementation reports in 12 councils. Quantitative data were analysed using SPSS, version 22 whereby descriptive and inferential statistics were performed. Qualitative data were analysed using ATLAS.ti version 8 where content analysis was performed. The study found that there is low implementation of biolarviciding in 75.0% of surveyed councils. All Vector Control Officers reported shortage of at least one type of resources, low community involvement (50.0%) and low level of community participation (83.33%). About 84.75% community members reported to have never participated in biolarviciding. Willingness to participate (AOR=2.73, P-value=0.046) and community involvement (AOR=5.49, P-value<0.001) were important predictors of community participation. Community members expressed high acceptance (80.25%) and willingness (77.75%) to participate in biolarviciding activities. Perceiving being at risk for malaria (AOR=2.68, P-value=0.001), malaria as a serious disease (AOR=3.09, P-value=0.001) and biolarviciding as an effective method for malaria reduction (AOR=4.07, P=0.002) were important predictors for community acceptance. Willingness to participate was associated with community acceptance (AOR=3.93, P-value<0.001) and perception that the participation will be valued (AOR=4.31, P<0.001). This study highlights resources inadequacy and low community participation as main barriers to implementation of biolarviciding. Improving commitment to supplying resources and strengthening community participation by involvement in all stages of implementation is crucial for successful and sustainable implementation.