The present exploratory study aimed to provide a more tangible and comprehensive picture of the construct of investment in language learning through investigating the issue from a quantitative perspective. To this end, the present researchers followed three main phases. First, a hypothesized model of investment in language learning with six components was developed for the Iranian English as a foreign language (EFL) learners based on the extensive readings of the literature on investment, consultations with a panel of experts, three university professors in the relevant fields, and interviews with 20 language learners. Second, a questionnaire was developed and validated based on the proposed model to represent its components. Finally, the data collected through this questionnaire were fed into the model to see to what extent the model fitted the data. The participants were male and female English language learners belonging to different age groups and English language proficiency levels.The initial results showed poor values; however, the model was trimmed by removing one item from the questionnaire, and final statistical indices showed that the model fitted the data.