This Book Constitutes The Refereed Proceedings Of The 11th International Conference Of The Clef Association, Clef 2020, Held In Thessaloniki, Greece, In September 2020.the Conference Has A Clear Focus On Experimental Information Retrieval With Special Attention To The Challenges Of Multimodality, Multilinguality, And Interactive Search Ranging From Unstructured To Semi Structures And Structured Data. The 5 Full Papers And 2 Short Papers Presented In This Volume Were Carefully Reviewed And Selected From 9 Submissions. This Year, The Contributions Addressed The Following Challenges: A Large-scale Evaluation Of Translation Effects In Academic Search, Advancement Of Assessor-driven Aggregation Methods For Efficient Relevance Assessments, And Development Of A New Test Dataset.