Language teaching has passed through a long way in search of a remedy for language learners and teachers. Countless theories, approaches, and methods have been recommended. With all these, however, more inclusive L2 theories and models ought to be considered to come up with real classroom practices. One of such crucial practices is authenticity, being straightforwardly found in web-based materials in general and Wikipedia texts and tasks in particular. In the same line and based on sound theoretical underpinnings, the place of Wikipedia is investigated in this study as a prospective tool to teach and learn a major language component with practical procedures i.e. vocabulary knowledge. To this end, 36 intermediate Iranian EFL students assigned to two control and experimental groups took part in the study. The results of the tests administered divulged that the learners in the Wikipedia group surpassed those of the control group. Hence, Wikipedia is considered as an encouraging authentic resource to assist EFL learners in improving their vocabulary knowledge. Implications of present findings and suggestions for further research are discussed.