The purpose of this study was to determine the relationship of Trade Unionism and Industrial relations in Oil and Gas companies in Niger Delta, Port Harcourt was the area of study picked and ten (10) Companies were chosen for this study. A sample size of one hundred and ninety-five (195) was gotten using Taro Yamane formula. The study is domiciled on industrial relations and trade unionism. Emphasis was made on the concepts of industrial relations and trade unionism with their dimensions streamlined. Furthermore, the study reviewed organizational culture as the moderator between industrial relations and trade unionism. The significance of the study is to make the result relevance to a set of individuals or group of persons that wishes to make related organizational and business decisions. Firstly, to managers of oil and gas manufacturing firms, especially in Niger-Delta and Practitioners in similar business line like government agencies within and outside the country. Secondly, the research result will benefit business-oriented students especially management and marketing students that will definitely draw inference from the reviews and the empirical evidence. Lastly, to workers in the oil and gas companies, the study will expand their horizon on the understanding of the importance and need to be in good relationships with employers thereby leading to enhancement of employee-employer mutual agreements.