This study appraised the effect of green marketing on sustainability of brewery firms in Nigeria using the South-East geo-political zone of Nigeria as the study area. Specifically, it sought to ascertain the extent green product; green price; green placement; and green promotion on the sustainability of breweries. The study was hinged on diffusion of innovation theory. Descriptive survey design using a sample size of 324 was adopted. Primary data used for the study were sourced with structured questionnaire, and analyzed in frequency tables and percentages, and multiple regression analysis for testing the hypotheses. The study found all the constructs of the study: green product, green price, green place (distribution), and green promotion to be significantly and positively related to sustainability of breweries in South-East of Nigeria. It concluded that green marketing significant positive effect on sustainability of breweries in South East of Nigeria. The study recommended that breweries in South-East Nigeria, and the broader Nigeria should sustain their environmental responsibilities and pay more attention to related issues so as to maintain their company sustainability.