The present study aims to investigate the effect of green marketing instruments and to understand the behavior of consumers in the purchase and use of e-books. The environmental label is one of the tools of green marketing that can be used in the primary pages of e-books to show being an environmentalist. This applied study is a survey-descriptive one in terms of collecting data. The population of the current study consists of 65 postgraduate students of the Department of Knowledge and Information Science of the University of Tehran in 2019, which 55 of them were selected by simple random sampling method using the Cochran's sample size formula with the confidence level of 0.05. A researcher-made questionnaire including 34 questions has been used to collect data. The Statistical Package for Social Sciences (SPSS) software was used to analyze and describe the data. The results showed that among the six measured parameters (i.e., 1. users' awareness of the environment; 2. users' environmental advocacy; 3. environmental advertising; 4. users' attitudes toward the environment; 5. users' purchase intention; and 6. environmental label), there is a meaningful and positive relationship between the four first above-mentioned parameters respectively and there is no meaningful relationship between fifth and sixth parameters. Based on the results of the present study, libraries, publishers and distributors of e-books are recommended to promote the environmental advocacy and green marketing to achieve their purpose in increasing the digital reading level of the country and to encourage users to choose the digital reading at a low cost, and also, help protect the environment and stop cutting down trees. Based on the results of the present research, we suggest to librarians and publishers of e-books to pay attention to users' awareness of the environment, users' environmental advocacy, environmental advertising, and users' attitudes toward the environment respectively.