This study examines the relationship between green supply chain management practices and productivity of manufacturing firms in Port Harcourt. Correlational survey design was adopted for this study. The population of this study is thirty-two (32) manufacturing companies in Rivers State which are registered with the Rivers State branch of Manufacturers Association of Nigeria (MAN). The study adopted the census population. 3 managers were selected from each firm multiplied by 32 firms gives us a total of ninety-two (92) for the study. Structured questionnaire instrument title the application of linear programming in assembly-line balancing of manufacturing firms in Port Harcourt questionnaire was developed on five-point likert scale. The result of the Cronbach's Alpha reliability test indicates .769 which is above .70 which implies that the items are reliable. PPMC (person product moment correlation) was used to test hypotheses on SPSS version 25. There is a significant relationship between green Design and productivity of manufacturing firms in Port Harcourt. There is a significant relationship between green Production and productivity of manufacturing firms in Port Harcourt. The study concluded that green supply chain management practices have a significant relationship with productivity of manufacturing firms in Port Harcourt. The study recommended Manufacturing firms in Port Harcourt should integrate sustainability considerations into their overall supply chain strategies to ensure that environmental concerns are addressed at every stage of the production process.