The purpose of this study is to investigate the effects of environmental knowledge and environmental concern on customer citizenship behavior, eco-friendly purchase intention, and eco-friendly activity. For this study, a survey was conducted using the snowball sampling method, and 243 of them were used for foodservice consumer questionnaires. The coded data were statistically analyzed using SPSS 24.0 and AMOS 24.0 programs. The result of the analysis is as following: Firstly, it was found that environmental knowledge and environmental interest had a positive(+) effect on customer civic behavior. Secondly, environmental knowledge and environmental interest were found to have a positive (+) effect on eco-friendly purchase intention. Thirdly, environmental knowledge and environmental interest were found to have a positive(+) effect on eco-friendly activities. These results support the results of previous studies that environmental knowledge and environmental interest are closely related to behaviors related to the environment. Therefore, this study identifies the effect of environmental knowledge and environmental concern on consumer behavior and presents implications for the marketing strategy of foodservice companies and the government's policy promotion plan. As a limitation of the study, the controlling variable should be considered since the size of their influence relationship may be controlled by a specific variable. The researchers did not consider differences in demographic characteristics. Therefore, in future research, it is necessary to conduct research in terms of identifying causal relationships by applying various demographic and usage characteristics.