ABSTRACT The study was carried out in Tanzania Electric Supply Company (TANESCO) along Morogoro Road, Dar -es -Salaam, Tanzania. The study focused on career development and organizational performance. The study was limited to career development which was characterized by management styles, succession planning, and training and organizational performance which were characterized by improved Quality of work lives, attraction of talent individuals, motivation and satisfaction basing on the period of January 2009 up to date. The study was guided by the following objectives: To examine the effects of management style on organizational perf01mance at Tanzania Electric Supply Company, to assess the effects of succession planning on the organizational performance at Tanzania Electric Supply Company and to examine the effects of training on organizational performance at Tanzania Electric Supply Company. The study adopted a case study research design the main purpose was to communicate a problem in more precious investigations and whereby both qualitative and quantitative methods of data analysis were used. Tanzania Electric Supply Company has a population of workforce of 4,896 persons. This consists of workforce from Tanzanian mainland and island of Zanzibar where they are in different depmiments such as engineering, finance, human resources, information technology and marketing. The study findings signposted that majority of the respondents in TANESCO 9 (or 30%) had worked for 06- 1 0 years and skilled. It revealed that employees had over stayed in the organization due to some activities such as training and succession planning and the research findings showed that the dominm1t management style was participative. Aligning on discoveries the following recommendations were proposed by the researcher: Career or job changes by employees in TANESCO should be based on the understanding of organizations' job descriptions, understand job posting systems, and selection policies. Coordinated, integrated efforts of the HR staffs, employees, managers and organizations are the key to success in cm·eer development at T ANESCO.