This book constitutes the refereed post-conference proceedings of the 4th International Workshop on Accelerator Programming Using Directives, WACCPD 2017, held in Denver, CO, USA, in November 2017. The 9 full papers presented have been carefully reviewed and selected from 14 submissions. The papers share knowledge and experiences to program emerging complex parallel computing systems. They are organized in the following three sections: applications; environments; and program evaluation.