Having a suitable organizational structure in place is a pre-requisite for the long term success of every business organization. Thus, the aim of this study was to investigate the effect of organizational structure on the performance of telecommunication companies in Enugu, Nigeria, with a focus on MTN Telecommunications PLC Enugu. The specific objectives however, were to; examine the effect of mechanistic structure on corporate goal attainment of MTN Telecommunications PLC Enugu, and also to ascertain the effect of organic structure on employees' commitment in MTN Telecommunications PLC Enugu. The population of the study was 121 main stream staff of MTN Enugu and in order to be truly representative, it was imperative to employ the entire population in conducting the study. Data were collected through questionnaire and oral interview. In the analysis, the study employed the Simple Linear Regression method using a 5% level of significance. And from the analysis, it was revealed that mechanistic structure negatively affect the performance of MTN Telecommunications PLC Enugu, and also that organic structure positively affect employees' commitment in MTN Telecommunications Enugu. Therefore, the study concluded that structure of an organization not only affect efficiency and productivity but also, morale and job satisfaction of employees' of the organization. Consequently, it was recommended that managers should adopt organizational structures that will enable them to successfully combine and maximize available resources for attainment of organizational goals.