This article concerns the effects of decentralization on service delivery in Jubek State of South Sudan. The study adopted both descriptive survey research design and explanatory research design to identify, analyze, and describe the relationship between governance decentralization and service delivery. The study population was 1890 local government officials from Jubek State. This study used multiphase sampling technique to select the subjects of study. Both stratified random sampling technique and simple random sampling techniques were adopted to get the sample of counties and local government officials to be included in the study. A sample of 330 respondents was selected for survey. Out of the 330 respondents, 275 completed the questionnaire survey giving a response rate of 83.3%. Cronbach's alpha was used to test for internal reliability of each variable used in the study. Data analysis was done using SPSS version 23 to generate descriptive statistics.The study used tables to analyze the association between governance decentralization dimensions and service delivery variables. The findings revealed that governance decentralization had a positive significant effect on service delivery in local governments in Jubek State, Southern Sudan. Specifically, the study found out that financial decentralization (mean 3.06 at Cronbach's alpha 0.703), administrative decentralization (mean 4.03 at Cronbach alpha 0.813), citizen participation (mean 3.57 at Cronbach alpha 0.702) and social accountability (mean 3.99 at Cronbach alpha 0.714) practices, for the 7 items examined, all had positive and significant effect on service delivery. However, social accountability had a significant effect on service delivery independently but not jointly. From these study findings, it is concluded that governance decentralization had a positive significant effect on service delivery. Thus the study makes a policy recommendation that the financial decentralization, administrative decentralization, citizen participation, social accountability practices need to be facilitated to improve service delivery in local government in Jubek State.