This research was born out of the desire to investigate the extent to which the second and fourth republic political parties impacted on national integration. As the great philosopher, Aristotle posited “man is a political animal”. This means that in every society, there must exist individual diverse interest and that of Nigeria is no exception Political parties are there to aggregate these diverse interests to make way for stability and national integration. To what extent have the political parties in second and fourth republic in Nigeria achieved this goals? And how did the structure of political parties in both republic promote private regarding interest? In order to effectively handle the matter I intend to look at the pre-1960 to early 1960s situation in Nigeria, this is to enable me have an adequate information on the genealogy of political parties in Nigeria to be able to find out whether the non-integrative nature of Nigeria political parties is caused by way these political parties were formed. At the course of investigation into this work I discovered that political parties in both republic were mostly formed and operated along ethnic lines. The structure of political parties in both republics appeared to have promoted private regarding interest. This led to ethnoregional domination and of course a number of imbalances in the party structure. The ethnic origin of these parties and their affiliations promoted private regarding interest which inhabited national integration. The work also proffered solutions to the problems that inhibited national integration and recommended ways through wtion and recommended ways through which political parties can help in solving the problem of national integration. An important feature of this research is the method of analysis, which is based on the historical explanation and method of logical assumption; certain lessons that are drawn from history could be relevant to the present and the future. For any research to be meaningful, reliable and scientific facts and ideas must be supplemented with empirical data. As such as substantial portion of this work would be gathered from the internet and journals. Secondary materials like Journals, Newspapers, Textbooks etc would also be used. Primary materials, which would also include party documents, would be also used.