The aim of this paper was investigating the effects of Organic knowledge, perceived consequences, subjective norms, price, and green trust, perceived consumer effectiveness, availability, relative advantage, and Organic purchase intention on Organic purchase behavior among Iranian consumers as the consumers in a developing country. The survey questionnaire was administered to the customers of large chain stores and Organic food stores in five provinces of Iran that had branches for producing and selling Organic food products. Given the very few number of Organic food consumers in Iran, only 192 out of 240 questionnaires were filled and then used as samples of study. In order to analysis the data and test the hypotheses, multiple regression analysis method was used using by SPSS software. Results showed strong support (R2=0.51) for the impact of price, consumer effectiveness, and perceived consequences on intention to purchase Organic food products. Organic knowledge, green trust, price, consumer effectiveness, and intention were found to have influenced purchase behavior. This paper will discuss the implications of these results for agricultural practitioners and marketers.