This book constitutes the refereed proceedings of the 12th International Conference on Similarity Search and Applications, SISAP 2019, held in Newark, NJ, USA, in October 2019.

The 12 full papers presented together with 18 short and 3 doctoral symposium papers were carefully reviewed and selected from 42 submissions. The papers are organized in topical sections named: Similarity Search and Retrieval; The Curse of Dimensionality; Clustering and Outlier Detection; Subspaces and Embeddings; Applications; Doctoral Symposium Papers.