In this study, the effect of freedom of reader choice on the incidental acquisition of vocabulary was investigated in English as a Foreign Language (EFL) reading classes. Despite advocating free extensive reading as a means of obtaining a native-like L2 vocabulary,existing studies investigating the incidental acquisition of vocabulary have not allowed for freedom of reader choice. Therefore, this study aims to address this issue by exploring two research questions: (1) Is incidental vocabulary acquisition affected by whether reading material is selected by the learner or assigned by a computer system; and (2) Is incidental vocabulary acquisition related to the learner’s level of interest in the reading materials? Results suggest that the influence of reader choice on students' L2 is worthy of teachers' attention, as is the influence of autonomy on students' L2 vocabulary acquisition. Moreover, this investigation shows the benefit of using computers to provide students with the freedom to choose the articles they read.