Prostate cancer (PCa) is a leading cause of cancer-related death in males. Aberrant expression of long noncoding RNAs (lncRNAs) is frequently reported in human malignancies. This study was performed to explore the role of LSAMP-AS1 in epithelial-mesenchymal transition (EMT), proliferation, migration and invasion of PCa cells. Initially, the differentially expressed lncRNAs in PCa were screened out by microarray analysis. The clinicopathological and prognostic significance of LSAMP-AS1 was evaluated. LSAMP-AS1 was over-expressed or silenced to investigate the roles in EMT, proliferation, migration and invasion of PCa cells. Moreover, the relationships between LSAMP-AS1 and miR-183-5p, as well as miR-183-5p and decorin (DCN) were characterized. The tumorigenicity of PCa cells was verified in nude mice. LSAMP-AS1 was poorly expressed in PCa tissues and cells. Low expression of LSAMP-AS1 was indicative of poor overall survival and disease-free survival, and related to Gleason score, TNM stage, and risk stratification. Over-expressed LSAMP-AS1 inhibited EMT, proliferation, migration and invasion of PCa cells, as well as tumor growth in nude mice. Meanwhile, over-expression of LSAMP-AS1 resulted in up-regulation of E-cadherin and down-regulation of Vimentin, N-cadherin, Ki67, PCNA, MMP-2, MMP-9, Ezrin and Fascin. Notably, LSAMP-AS1 competitively bound to miR-183-5p which directly targets DCN. It was confirmed that the inhibitory effect of LSAMP-AS1 on PCa cells was achieved by binding to miR-183-5p, thus promoting the expression of DCN. LSAMP-AS1 up-regulates the DCN gene by competitively binding to miR-183-5p, thus inhibiting EMT, proliferation, migration and invasion of PCa cells. Copyright © 2019 The Author(s). Published by Elsevier B.V. All rights reserved.