The study examined the relationship between project complexity management, knowledge resources and project performance of Umeme’s SCADA, Yaka and AMR projects. This study was a cross-sectional research design which applied a quantitative research approach. Data was obtained from 67 employees of UMEME Ltd using a structured questionnaire instrument. Validity of the questionnaire was obtained through expert judgment and content validity index. Reliability on the other hand was obtained using pretesting and Cronbach’s alpha coefficient. Data obtained from respondents was cleaned, edited, coded and captured in SPSS (v. 25) for analysis obtaining descriptive and inferential statistics for interpreting results. A Med Graph was also applied to test mediation. This study found out a positive relationship between project complexity management and project performance of Umeme’s SCADA, Yaka and AMR projects. There was a positive relationship between project complexity management and knowledge resources among Umeme’s SCADA, Yaka and AMR projects. Furthermore, the study found a positive relationship between knowledge resources and project performance of Umeme’s SCADA, Yaka and AMR projects. This study established that both project complex management and knowledge resources significantly predict project performance. The better predictor was project complexity management. Additionally, the study found that knowledge resources partially mediate the relationship between project complexity management and project performance of management of Umeme’s SCADA, Yaka and AMR projects. The study concludes that project complexity management and knowledge resources are crucial are important in determining project performance. This study recommends enhancing minimizing complexity associated with projects and boosting knowledge resources to boost project performance.