This book constitutes the refereed proceedings of the 15th International Conference on Web Information Systems and Applications, WISA 2018, held in Taiyuan, China, in September 2018. The 29 full papers presented together with 16 short papers were carefully reviewed and selected from 103 submissions. The papers cover topics such as machine learning and data mining; cloud computing and big data; information retrieval; natural language processing; data privacy and security; knowledge graphs and social networks; query processing; and recommendations.