This study investigated the impact of manpower development on the performance of workers in government institutions in Nigeria – a case study of the independent national electoral commission, Imo State. To this effect, three hypotheses were formulated and tested to determine the effect of manpower development on independent national electoral commission staff in Imo State. The related literature was reviewed. A questionnaire was used to collect data from 100 respondents from INEC offices across the twenty-seven local government area of Imo State. The data collected were statistically analyzed using chi-square for the three hypotheses at the degree of freedom both involved a 0.05 level of significance. The result of the findings indicated that the staff of the Independent National Electoral Commission, Imo State who had in one time or the other taken an active part in any manpower development will relatively perform effectively, acquires skills and discharge the INEC functions satisfactorily. Based on the findings, the researcher, therefore, recommends that manpower development should be a compulsory programme for all staff for efficiency and effectiveness.