This book constitutes the refereed proceedings of the 6th International Conference of the CLEF Initiative, CLEF 2015, held in Toulouse, France, in September 2015. The 31 full papers and 20 short papers presented were carefully reviewed and selected from 68 submissions. They cover a broad range of issues in the fields of multilingual and multimodal information access evaluation, also included are a set of labs and workshops designed to test different aspects of mono and cross-language information retrieval systems.