This thesis is a study of Project-based Learning (PBL) as a supplement to mainstream foreign language courses at the university level.The shift in emphasis in language teaching from a teacher-directed approach to a learner-centered one, along with the perceived need to promote learners’ efforts at improving linguistic competence, has resulted in new challenges for language teachers. How to sustain student engagement in language learning, how to develop learner autonomy and general academic skills have gone beyond the rationale of traditional textbooks.By carrying out experiments with 210 undergraduate students, the present study tries to explore the possible gains in students’ linguistic proficiency and increased autonomy through a PBL approach. The findings of the present study indicate that when taking responsibility for the learning process, interacting with cognitively and linguistically demanding contexts, the students find the learning meaningful and authentic. There are reported significant gains in reading, writing, speaking and listening. Analysis of the student products shows application of more complex analytical and critical skills, larger vocabulary, complex sentences, variety of structures and better coherence. The students also find increased autonomy and greater confidence in future independent learning, and last but not the least, greater happiness in collaborating with group members.