This paper attempts to study the knowledge-sharing behaviors of Iranian professionals in cyberspace. To this end, semi-structured interviews, Delphi method and an online questionnaire were used as research tools through qualitative and quantitative methods. Since the main research tools were semi-structured interviews with 15 experts to meet the research purposes, the process was continued until the “theoretical saturation” was realized. Afterwards, in order to approve or amend the obtained indices from the analysis of interview texts, the Delphi method was used. Hence, the knowledge-sharing behavior model was extracted. Through chain sampling, the selected network users, 299 electronic questionnaires were collected and analyzed using Smart PLS software and confirmatory factor analysis (rate of return, 77%). The findings indicate that the main variables of knowledge-sharing behaviors are divided into individual, group, and environmental indices respectively. Components of the individual dimension of knowledge-sharing include motivation, ethicality, personality, ability, attitude towards knowledge-sharing and psychological security. Group dimension of knowledge-sharing include shared benefits, group structure and social capital and finally environmental factors, including technological (technical requirements of specialized social networks), political rights (the country's cyberspace policy), economic (cost and variety of internet packages), socio-cultural (expert lifestyle and national character).